Managing State

Hyper Text Transfer Protocol (HTTP) is a stateless protocol. When the client disconnects from the server, the ASP.NET engine discards the page objects. This way, each web application can scale up to serve numerous requests simultaneously without running out of server memory.

However, there needs to be some technique to store the information between requests and to retrieve it when required. This information i.e., the current value of all the controls and variables for the current user in the current session is called the State.

ASP.NET manages four types of states:

View State
Control State
Session State
Application State

View State

The view state is the state of the page and all its controls. It is automatically maintained across posts by the ASP.NET framework.

When a page is sent back to the client, the changes in the properties of the page and its controls are determined, and stored in the value of a hidden input field named _VIEWSTATE. When the page is again posted back, the _VIEWSTATE field is sent to the server with the HTTP request.

The view state could be enabled or disabled for:

The entire application by setting the EnableViewState property in the <pages> section of web.config file.
A page by setting the EnableViewState attribute of the Page directive, as <%@ Page Language="C#" EnableViewState="false" %>
A control by setting the Control.EnableViewState property.

It is implemented using a view state object defined by the StateBag class which defines a collection of view state items. The state bag is a data structure containing attribute value pairs, stored as strings associated with objects.

The StateBag class has the following properties:

Properties	Description
Item(name)	The value of the view state item with the specified name. This is the default property of the StateBag class.
Count	The number of items in the view state collection.
Keys	Collection of keys for all the items in the collection.
Values	Collection of values for all the items in the collection.

The StateBag class has the following methods:

Methods	Description
Add(name, value)	Adds an item to the view state collection and existing item is updated.
Clear	Removes all the items from the collection.
Equals(Object)	Determines whether the specified object is equal to the current object.
Finalize	Allows it to free resources and perform other cleanup operations.
GetEnumerator	Returns an enumerator that iterates over all the key/value pairs of the StateItem objects stored in the StateBag object.
GetType	Gets the type of the current instance.
IsItemDirty	Checks a StateItem object stored in the StateBag object to evaluate whether it has been modified.
Remove(name)	Removes the specified item.
SetDirty	Sets the state of the StateBag object as well as the Dirty property of each of the StateItem objects contained by it.
SetItemDirty	Sets the Dirty property for the specified StateItem object in the StateBag object.
ToString	Returns a string representing the state bag object.

Example

The following example demonstrates the concept of storing view state. Let us keep a counter, which is incremented each time the page is posted back by clicking a button on the page. A label control shows the value in the counter.

The markup file code is as follows:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="statedemo._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
      
         <div>
            <h3>View State demo</h3>
         
            Page Counter:
            
            <asp:Label ID="lblCounter" runat="server" />
            <asp:Button ID="btnIncrement" runat="server" Text="Add Count" onclick="btnIncrement_Click" />
         </div>
         
      </form>
   </body>
   
</html>

The code behind file for the example is shown here:

public partial class _Default : System.Web.UI.Page
{
   public int counter
   {
      get
      {
         if (ViewState["pcounter"] != null)
         {
            return ((int)ViewState["pcounter"]);
         }
         else
         {
            return 0;
         }
      }
      
      set
      {
         ViewState["pcounter"] = value;
      }
   }
        
   protected void Page_Load(object sender, EventArgs e)
   {
      lblCounter.Text = counter.ToString();
      counter++;
   }
}

It would produce the following result:

View State Demo

Control State

Control state cannot be modified, accessed directly, or disabled.

Session State

When a user connects to an ASP.NET website, a new session object is created. When session state is turned on, a new session state object is created for each new request. This session state object becomes part of the context and it is available through the page.

Session state is generally used for storing application data such as inventory, supplier list, customer record, or shopping cart. It can also keep information about the user and his preferences, and keep the track of pending operations.

Sessions are identified and tracked with a 120-bit SessionID, which is passed from client to server and back as cookie or a modified URL. The SessionID is globally unique and random.

The session state object is created from the HttpSessionState class, which defines a collection of session state items.

The HttpSessionState class has the following properties:

Properties	Description
SessionID	The unique session identifier.
Item(name)	The value of the session state item with the specified name. This is the default property of the HttpSessionState class.
Count	The number of items in the session state collection.
TimeOut	Gets and sets the amount of time, in minutes, allowed between requests before the session-state provider terminates the session.

The HttpSessionState class has the following methods:

Methods	Description
Add(name, value)	Adds an item to the session state collection.
Clear	Removes all the items from session state collection.
Remove(name)	Removes the specified item from the session state collection.
RemoveAll	Removes all keys and values from the session-state collection.
RemoveAt	Deletes an item at a specified index from the session-state collection.

The session state object is a name-value pair to store and retrieve some information from the session state object. You could use the following code for the same:

void StoreSessionInfo()
{
   String fromuser = TextBox1.Text;
   Session["fromuser"] = fromuser;
}

void RetrieveSessionInfo()
{
   String fromuser = Session["fromuser"];
   Label1.Text = fromuser;
}

The above code stores only strings in the Session dictionary object, however, it can store all the primitive data types and arrays composed of primitive data types, as well as the DataSet, DataTable, HashTable, and Image objects, as well as any user-defined class that inherits from the ISerializable object.

Example

The following example demonstrates the concept of storing session state. There are two buttons on the page, a text box to enter string and a label to display the text stored from last session.

The mark up file code is as follows:

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default"  %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
         <div>
            &nbsp; &nbsp; &nbsp;
            
            <table style="width: 568px; height: 103px">
            
               <tr>
                  <td style="width: 209px">
                     <asp:Label ID="lblstr" runat="server" Text="Enter a String"  style="width:94px">
                     </asp:Label>
                  </td>
					
                  <td style="width: 317px">
                     <asp:TextBox ID="txtstr" runat="server" style="width:227px">
                     </asp:TextBox>
                  </td>
               </tr>
	
               <tr>
                  <td style="width: 209px"> </td>
                  <td style="width: 317px"> </td>
               </tr>
	
               <tr>
                  <td style="width: 209px">
                     <asp:Button ID="btnnrm" runat="server" 
                        Text="No action button" style="width:128px" />
                  </td>
	
                  <td style="width: 317px">
                     <asp:Button ID="btnstr" runat="server" 
                        OnClick="btnstr_Click" Text="Submit the String" />
                  </td> 
               </tr>
	
               <tr>
                  <td style="width: 209px">  </td>
	
                  <td style="width: 317px">  </td>  
               </tr>
	
               <tr>
                  <td style="width: 209px">
                     <asp:Label ID="lblsession" runat="server"  style="width:231px"  >
                     </asp:Label>
                  </td>
	
                  <td style="width: 317px">  </td>
               </tr>
	
               <tr>
                  <td style="width: 209px">
                     <asp:Label ID="lblshstr" runat="server">
                     </asp:Label>
                  </td>
	
                  <td style="width: 317px">  </td>
               </tr>
               
            </table>
            
         </div>
      </form>
   </body>
</html>

It should look like the following in design view:

session design view

The code behind file is given here:

public partial class _Default : System.Web.UI.Page 
{
   String mystr;
   
   protected void Page_Load(object sender, EventArgs e)
   {
      this.lblshstr.Text = this.mystr;
      this.lblsession.Text = (String)this.Session["str"];
   }
   
   protected void btnstr_Click(object sender, EventArgs e)
   {
      this.mystr = this.txtstr.Text;
      this.Session["str"] = this.txtstr.Text;
      this.lblshstr.Text = this.mystr;
      this.lblsession.Text = (String)this.Session["str"];
   }
}

Execute the file and observe how it works:

session run view

Application State

The ASP.NET application is the collection of all web pages, code and other files within a single virtual directory on a web server. When information is stored in application state, it is available to all the users.

To provide for the use of application state, ASP.NET creates an application state object for each application from the HTTPApplicationState class and stores this object in server memory. This object is represented by class file global.asax.

Application State is mostly used to store hit counters and other statistical data, global application data like tax rate, discount rate etc. and to keep the track of users visiting the site.

The HttpApplicationState class has the following properties:

Properties	Description
Item(name)	The value of the application state item with the specified name. This is the default property of the HttpApplicationState class.
Count	The number of items in the application state collection.

The HttpApplicationState class has the following methods:

Methods	Description
Add(name, value)	Adds an item to the application state collection.
Clear	Removes all the items from the application state collection.
Remove(name)	Removes the specified item from the application state collection.
RemoveAll	Removes all objects from an HttpApplicationState collection.
RemoveAt	Removes an HttpApplicationState object from a collection by index.
Lock()	Locks the application state collection so only the current user can access it.
Unlock()	Unlocks the application state collection so all the users can access it.

Application state data is generally maintained by writing handlers for the events:

Application_Start
Application_End
Application_Error
Session_Start
Session_End

The following code snippet shows the basic syntax for storing application state information:

Void Application_Start(object sender, EventArgs e)
{
   Application["startMessage"] = "The application has started.";
}

Void Application_End(object sender, EventArgs e)
{
   Application["endtMessage"] = "The application has ended.";

Validators

ASP.NET validation controls validate the user input data to ensure that useless, unauthenticated, or contradictory data don't get stored.

ASP.NET provides the following validation controls:

RequiredFieldValidator
RangeValidator
CompareValidator
RegularExpressionValidator
CustomValidator
ValidationSummary

BaseValidator Class

The validation control classes are inherited from the BaseValidator class hence they inherit its properties and methods. Therefore, it would help to take a look at the properties and the methods of this base class, which are common for all the validation controls:

Members	Description
ControlToValidate	Indicates the input control to validate.
Display	Indicates how the error message is shown.
EnableClientScript	Indicates whether client side validation will take.
Enabled	Enables or disables the validator.
ErrorMessage	Indicates error string.
Text	Error text to be shown if validation fails.
IsValid	Indicates whether the value of the control is valid.
SetFocusOnError	It indicates whether in case of an invalid control, the focus should switch to the related input control.
ValidationGroup	The logical group of multiple validators, where this control belongs.
Validate()	This method revalidates the control and updates the IsValid property.

RequiredFieldValidator Control

The RequiredFieldValidator control ensures that the required field is not empty. It is generally tied to a text box to force input into the text box.

The syntax of the control is as given:

<asp:RequiredFieldValidator ID="rfvcandidate" 
   runat="server" ControlToValidate ="ddlcandidate"
   ErrorMessage="Please choose a candidate" 
   InitialValue="Please choose a candidate">
   
</asp:RequiredFieldValidator>

RangeValidator Control

The RangeValidator control verifies that the input value falls within a predetermined range.

It has three specific properties:

Properties	Description
Type	It defines the type of the data. The available values are: Currency, Date, Double, Integer, and String.
MinimumValue	It specifies the minimum value of the range.
MaximumValue	It specifies the maximum value of the range.

The syntax of the control is as given:

<asp:RangeValidator ID="rvclass" runat="server" ControlToValidate="txtclass" 
   ErrorMessage="Enter your class (6 - 12)" MaximumValue="12" 
   MinimumValue="6" Type="Integer">
   
</asp:RangeValidator>

CompareValidator Control

The CompareValidator control compares a value in one control with a fixed value or a value in another control.

It has the following specific properties:

Properties	Description
Type	It specifies the data type.
ControlToCompare	It specifies the value of the input control to compare with.
ValueToCompare	It specifies the constant value to compare with.
Operator	It specifies the comparison operator, the available values are: Equal, NotEqual, GreaterThan, GreaterThanEqual, LessThan, LessThanEqual, and DataTypeCheck.

The basic syntax of the control is as follows:

<asp:CompareValidator ID="CompareValidator1" runat="server" 
   ErrorMessage="CompareValidator">
   
</asp:CompareValidator>

RegularExpressionValidator

The RegularExpressionValidator allows validating the input text by matching against a pattern of a regular expression. The regular expression is set in the ValidationExpression property.

The following table summarizes the commonly used syntax constructs for regular expressions:

Character Escapes	Description
\b	Matches a backspace.
\t	Matches a tab.
\r	Matches a carriage return.
\v	Matches a vertical tab.
\f	Matches a form feed.
\n	Matches a new line.
\	Escape character.

Apart from single character match, a class of characters could be specified that can be matched, called the metacharacters.

Metacharacters	Description
.	Matches any character except \n.
[abcd]	Matches any character in the set.
[^abcd]	Excludes any character in the set.
[2-7a-mA-M]	Matches any character specified in the range.
\w	Matches any alphanumeric character and underscore.
\W	Matches any non-word character.
\s	Matches whitespace characters like, space, tab, new line etc.
\S	Matches any non-whitespace character.
\d	Matches any decimal character.
\D	Matches any non-decimal character.

Quantifiers could be added to specify number of times a character could appear.

Quantifier	Description
*	Zero or more matches.
+	One or more matches.
?	Zero or one matches.
{N}	N matches.
{N,}	N or more matches.
{N,M}	Between N and M matches.

The syntax of the control is as given:

<asp:RegularExpressionValidator ID="string" runat="server" ErrorMessage="string"
   ValidationExpression="string" ValidationGroup="string">
   
</asp:RegularExpressionValidator>

CustomValidator

The CustomValidator control allows writing application specific custom validation routines for both the client side and the server side validation.

The client side validation is accomplished through the ClientValidationFunction property. The client side validation routine should be written in a scripting language, such as JavaScript or VBScript, which the browser can understand.

The server side validation routine must be called from the control's ServerValidate event handler. The server side validation routine should be written in any .Net language, like C# or VB.Net.

The basic syntax for the control is as given:

<asp:CustomValidator ID="CustomValidator1" runat="server" 
   ClientValidationFunction=.cvf_func. ErrorMessage="CustomValidator">
   
</asp:CustomValidator>

ValidationSummary

The ValidationSummary control does not perform any validation but shows a summary of all errors in the page. The summary displays the values of the ErrorMessage property of all validation controls that failed validation.

The following two mutually inclusive properties list out the error message:

ShowSummary : shows the error messages in specified format.
ShowMessageBox : shows the error messages in a separate window.

The syntax for the control is as given:

<asp:ValidationSummary ID="ValidationSummary1" runat="server" 
   DisplayMode = "BulletList" ShowSummary = "true" HeaderText="Errors:" />

Validation Groups

Complex pages have different groups of information provided in different panels. In such situation, a need might arise for performing validation separately for separate group. This kind of situation is handled using validation groups.

To create a validation group, you should put the input controls and the validation controls into the same logical group by setting their ValidationGroup property.

Example

The following example describes a form to be filled up by all the students of a school, divided into four houses, for electing the school president. Here, we use the validation controls to validate the user input.

This is the form in design view:

form in Design view

The content file code is as given:

<form id="form1" runat="server">

   <table style="width: 66%;">
   
      <tr>
         <td class="style1" colspan="3" align="center">
         <asp:Label ID="lblmsg" 
            Text="President Election Form : Choose your president" 
            runat="server" />
         </td>
      </tr>

      <tr>
         <td class="style3">
            Candidate:
         </td>

         <td class="style2">
            <asp:DropDownList ID="ddlcandidate" runat="server"  style="width:239px">
               <asp:ListItem>Please Choose a Candidate</asp:ListItem>
               <asp:ListItem>M H Kabir</asp:ListItem>
               <asp:ListItem>Steve Taylor</asp:ListItem>
               <asp:ListItem>John Abraham</asp:ListItem>
               <asp:ListItem>Venus Williams</asp:ListItem>
            </asp:DropDownList>
         </td>

         <td>
            <asp:RequiredFieldValidator ID="rfvcandidate" 
               runat="server" ControlToValidate ="ddlcandidate"
               ErrorMessage="Please choose a candidate" 
               InitialValue="Please choose a candidate">
            </asp:RequiredFieldValidator>
         </td>
      </tr>

      <tr>
         <td class="style3">
            House:
         </td>

         <td class="style2">
            <asp:RadioButtonList ID="rblhouse" runat="server" RepeatLayout="Flow">
               <asp:ListItem>Red</asp:ListItem>
               <asp:ListItem>Blue</asp:ListItem>
               <asp:ListItem>Yellow</asp:ListItem>
               <asp:ListItem>Green</asp:ListItem>
            </asp:RadioButtonList>
         </td>

         <td>
            <asp:RequiredFieldValidator ID="rfvhouse" runat="server" 
               ControlToValidate="rblhouse" ErrorMessage="Enter your house name" >
            </asp:RequiredFieldValidator>
            <br />
         </td>
      </tr>

      <tr>
         <td class="style3">
            Class:
         </td>

         <td class="style2">
            <asp:TextBox ID="txtclass" runat="server"></asp:TextBox>
         </td>

         <td>
            <asp:RangeValidator ID="rvclass" 
               runat="server" ControlToValidate="txtclass" 
               ErrorMessage="Enter your class (6 - 12)" MaximumValue="12" 
               MinimumValue="6" Type="Integer">
            </asp:RangeValidator>
         </td>
      </tr>

      <tr>
         <td class="style3">
            Email:
         </td>

         <td class="style2">
            <asp:TextBox ID="txtemail" runat="server" style="width:250px">
            </asp:TextBox>
         </td>

         <td>
            <asp:RegularExpressionValidator ID="remail" runat="server" 
               ControlToValidate="txtemail" ErrorMessage="Enter your email" 
               ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*">
            </asp:RegularExpressionValidator>
         </td>
      </tr>

      <tr>
         <td class="style3" align="center" colspan="3">
            <asp:Button ID="btnsubmit" runat="server" onclick="btnsubmit_Click" 
               style="text-align: center" Text="Submit" style="width:140px" />
         </td>
      </tr>
   </table>
   <asp:ValidationSummary ID="ValidationSummary1" runat="server" 
      DisplayMode ="BulletList" ShowSummary ="true" HeaderText="Errors:" />
</form>

The code behind the submit button:

protected void btnsubmit_Click(object sender, EventArgs e)
{
   if (Page.IsValid)
   {
      lblmsg.Text = "Thank You";
   }
   else
   {
      lblmsg.Text = "Fill up all the fields";
   }
}

Database Access

ASP.NET allows the following sources of data to be accessed and used:

Databases (e.g., Access, SQL Server, Oracle, MySQL)
XML documents
Business Objects
Flat files

ASP.NET hides the complex processes of data access and provides much higher level of classes and objects through which data is accessed easily. These classes hide all complex coding for connection, data retrieving, data querying, and data manipulation.

ADO.NET is the technology that provides the bridge between various ASP.NET control objects and the backend data source. In this tutorial, we will look at data access and working with the data in brief.

Retrieve and display data

It takes two types of data controls to retrieve and display data in ASP.NET:

A data source control - It manages the connection to the data, selection of data, and other jobs such as paging and caching of data etc.
A data view control - It binds and displays the data and allows data manipulation.

We will discuss the data binding and data source controls in detail later. In this section, we will use a SqlDataSource control to access data and a GridView control to display and manipulate data in this chapter.

We will also use an Access database, which contains the details about .Net books available in the market. Name of our database is ASPDotNetStepByStep.mdb and we will use the data table DotNetReferences.

The table has the following columns: ID, Title, AuthorFirstName, AuthorLastName, Topic, and Publisher.

Here is a snapshot of the data table:

Data Table

Let us directly move to action, take the following steps:

(1) Create a web site and add a SqlDataSourceControl on the web form.

SqlDataSourceControl

(2) Click on the Configure Data Source option.

Configure Data Source

(3) Click on the New Connection button to establish connection with a database.

Connection with a database

(4) Once the connection is set up, you may save it for further use. At the next step, you are asked to configure the select statement:

Select statement

(5) Select the columns and click next to complete the steps. Observe the WHERE, ORDER BY, and the Advanced buttons. These buttons allow you to provide the where clause, order by clause, and specify the insert, update, and delete commands of SQL respectively. This way, you can manipulate the data.

(6) Add a GridView control on the form. Choose the data source and format the control using AutoFormat option.

AutoFormat

(7) After this the formatted GridView control displays the column headings, and the application is ready to execute.

GridView control

(8) Finally execute the application.

Database Result

The content file code is as given:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="dataaccess.aspx.cs" 
   Inherits="datacaching.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
         <div>
         
            <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
               ConnectionString= "<%$   ConnectionStrings:ASPDotNetStepByStepConnectionString%>" 
               ProviderName= "<%$ ConnectionStrings:
                  ASPDotNetStepByStepConnectionString.ProviderName %>" 
               SelectCommand="SELECT [Title], [AuthorLastName], 
                  [AuthorFirstName], [Topic] FROM [DotNetReferences]">
            </asp:SqlDataSource>
            
            <asp:GridView ID="GridView1" runat="server" 
               AutoGenerateColumns="False" CellPadding="4" 
               DataSourceID="SqlDataSource1" ForeColor="#333333" 
               GridLines="None">
               <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
            
               <Columns>
                  <asp:BoundField DataField="Title" HeaderText="Title" 
                     SortExpression="Title" />
                  <asp:BoundField DataField="AuthorLastName" 
                     HeaderText="AuthorLastName" SortExpression="AuthorLastName" />
                  <asp:BoundField DataField="AuthorFirstName" 
                     HeaderText="AuthorFirstName" SortExpression="AuthorFirstName" />
                  <asp:BoundField DataField="Topic" 
                     HeaderText="Topic" SortExpression="Topic" />
               </Columns>
               <FooterStyle BackColor="#5D7B9D" 
                  Font-Bold="True" ForeColor="White" />
               <PagerStyle BackColor="#284775" 
                  ForeColor="White" HorizontalAlign="Center" />
               <SelectedRowStyle BackColor="#E2DED6" 
                  Font-Bold="True" ForeColor="#333333" />
               <HeaderStyle BackColor="#5D7B9D" Font-Bold="True"  
                  ForeColor="White" />
               <EditRowStyle BackColor="#999999" />
               <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
            </asp:GridView>
         </div>
      </form>
   </body>
</html>

ADO.net

ADO.NET provides a bridge between the front end controls and the back end database. The ADO.NET objects encapsulate all the data access operations and the controls interact with these objects to display data, thus hiding the details of movement of data.

The following figure shows the ADO.NET objects at a glance:

ADO.Net objects

The DataSet Class

The dataset represents a subset of the database. It does not have a continuous connection to the database. To update the database a reconnection is required. The DataSet contains DataTable objects and DataRelation objects. The DataRelation objects represent the relationship between two tables.

Following table shows some important properties of the DataSet class:

Properties	Description
CaseSensitive	Indicates whether string comparisons within the data tables are case-sensitive.
Container	Gets the container for the component.
DataSetName	Gets or sets the name of the current data set.
DefaultViewManager	Returns a view of data in the data set.
DesignMode	Indicates whether the component is currently in design mode.
EnforceConstraints	Indicates whether constraint rules are followed when attempting any update operation.
Events	Gets the list of event handlers that are attached to this component.
ExtendedProperties	Gets the collection of customized user information associated with the DataSet.
HasErrors	Indicates if there are any errors.
IsInitialized	Indicates whether the DataSet is initialized.
Locale	Gets or sets the locale information used to compare strings within the table.
Namespace	Gets or sets the namespace of the DataSet.
Prefix	Gets or sets an XML prefix that aliases the namespace of the DataSet.
Relations	Returns the collection of DataRelation objects.
Tables	Returns the collection of DataTable objects.

The following table shows some important methods of the DataSet class:

Methods	Description
AcceptChanges	Accepts all changes made since the DataSet was loaded or this method was called.
BeginInit	Begins the initialization of the DataSet. The initialization occurs at run time.
Clear	Clears data.
Clone	Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
Copy	Copies both structure and data.
CreateDataReader()	Returns a DataTableReader with one result set per DataTable, in the same sequence as the tables appear in the Tables collection.
CreateDataReader(DataTable[])	Returns a DataTableReader with one result set per DataTable.
EndInit	Ends the initialization of the data set.
Equals(Object)	Determines whether the specified Object is equal to the current Object.
Finalize	Free resources and perform other cleanups.
GetChanges	Returns a copy of the DataSet with all changes made since it was loaded or the AcceptChanges method was called.
GetChanges(DataRowState)	Gets a copy of DataSet with all changes made since it was loaded or the AcceptChanges method was called, filtered by DataRowState.
GetDataSetSchema	Gets a copy of XmlSchemaSet for the DataSet.
GetObjectData	Populates a serialization information object with the data needed to serialize the DataSet.
GetType	Gets the type of the current instance.
GetXML	Returns the XML representation of the data.
GetXMLSchema	Returns the XSD schema for the XML representation of the data.
HasChanges()	Gets a value indicating whether the DataSet has changes, including new, deleted, or modified rows.
HasChanges(DataRowState)	Gets a value indicating whether the DataSet has changes, including new, deleted, or modified rows, filtered by DataRowState.
IsBinarySerialized	Inspects the format of the serialized representation of the DataSet.
Load(IDataReader, LoadOption, DataTable[])	Fills a DataSet with values from a data source using the supplied IDataReader, using an array of DataTable instances to supply the schema and namespace information.
Load(IDataReader, LoadOption, String[])	Fills a DataSet with values from a data source using the supplied IDataReader, using an array of strings to supply the names for the tables within the DataSet.
Merge()	Merges the data with data from another DataSet. This method has different overloaded forms.
ReadXML()	Reads an XML schema and data into the DataSet. This method has different overloaded forms.
ReadXMLSchema(0)	Reads an XML schema into the DataSet. This method has different overloaded forms.
RejectChanges	Rolls back all changes made since the last call to AcceptChanges.
WriteXML()	Writes an XML schema and data from the DataSet. This method has different overloaded forms.
WriteXMLSchema()	Writes the structure of the DataSet as an XML schema. This method has different overloaded forms.

The DataTable Class

The DataTable class represents the tables in the database. It has the following important properties; most of these properties are read only properties except the PrimaryKey property:

Properties	Description
ChildRelations	Returns the collection of child relationship.
Columns	Returns the Columns collection.
Constraints	Returns the Constraints collection.
DataSet	Returns the parent DataSet.
DefaultView	Returns a view of the table.
ParentRelations	Returns the ParentRelations collection.
PrimaryKey	Gets or sets an array of columns as the primary key for the table.
Rows	Returns the Rows collection.

The following table shows some important methods of the DataTable class:

Methods	Description
AcceptChanges	Commits all changes since the last AcceptChanges.
Clear	Clears all data from the table.
GetChanges	Returns a copy of the DataTable with all changes made since the AcceptChanges method was called.
GetErrors	Returns an array of rows with errors.
ImportRows	Copies a new row into the table.
LoadDataRow	Finds and updates a specific row, or creates a new one, if not found any.
Merge	Merges the table with another DataTable.
NewRow	Creates a new DataRow.
RejectChanges	Rolls back all changes made since the last call to AcceptChanges.
Reset	Resets the table to its original state.
Select	Returns an array of DataRow objects.

The DataRow Class

The DataRow object represents a row in a table. It has the following important properties:

Properties	Description
HasErrors	Indicates if there are any errors.
Items	Gets or sets the data stored in a specific column.
ItemArrays	Gets or sets all the values for the row.
Table	Returns the parent table.

The following table shows some important methods of the DataRow class:

Methods	Description
AcceptChanges	Accepts all changes made since this method was called.
BeginEdit	Begins edit operation.
CancelEdit	Cancels edit operation.
Delete	Deletes the DataRow.
EndEdit	Ends the edit operation.
GetChildRows	Gets the child rows of this row.
GetParentRow	Gets the parent row.
GetParentRows	Gets parent rows of DataRow object.
RejectChanges	Rolls back all changes made since the last call to AcceptChanges.

The DataAdapter Object

The DataAdapter object acts as a mediator between the DataSet object and the database. This helps the Dataset to contain data from multiple databases or other data source.

The DataReader Object

The DataReader object is an alternative to the DataSet and DataAdapter combination. This object provides a connection oriented access to the data records in the database. These objects are suitable for read-only access, such as populating a list and then breaking the connection.

DbCommand and DbConnection Objects

The DbConnection object represents a connection to the data source. The connection could be shared among different command objects.

The DbCommand object represents the command or a stored procedure sent to the database from retrieving or manipulating data.

Example

So far, we have used tables and databases already existing in our computer. In this example, we will create a table, add column, rows and data into it and display the table using a GridView object.

The source file code is as given:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="createdatabase._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
      
         <div>
            <asp:GridView ID="GridView1" runat="server">
            </asp:GridView>
         </div>
         
      </form>
   </body>
   
</html>

The code behind file is as given:

namespace createdatabase
{
   public partial class _Default : System.Web.UI.Page
   {
      protected void Page_Load(object sender, EventArgs e)
      {
         if (!IsPostBack)
         {
            DataSet ds = CreateDataSet();
            GridView1.DataSource = ds.Tables["Student"];
            GridView1.DataBind();
         }
      }
      
      private DataSet CreateDataSet()
      {
         //creating a DataSet object for tables
         DataSet dataset = new DataSet();

         // creating the student table
         DataTable Students = CreateStudentTable();
         dataset.Tables.Add(Students);
         return dataset;
      }
      
      private DataTable CreateStudentTable()
      {
         DataTable Students = new DataTable("Student");

         // adding columns
         AddNewColumn(Students, "System.Int32", "StudentID");
         AddNewColumn(Students, "System.String", "StudentName");
         AddNewColumn(Students, "System.String", "StudentCity");

         // adding rows
         AddNewRow(Students, 1, "M H Kabir", "Kolkata");
         AddNewRow(Students, 1, "Shreya Sharma", "Delhi");
         AddNewRow(Students, 1, "Rini Mukherjee", "Hyderabad");
         AddNewRow(Students, 1, "Sunil Dubey", "Bikaner");
         AddNewRow(Students, 1, "Rajat Mishra", "Patna");

         return Students;
      }

      private void AddNewColumn(DataTable table, string columnType, string  columnName)
      {
         DataColumn column = table.Columns.Add(columnName,  Type.GetType(columnType));
      }

      //adding data into the table
      private void AddNewRow(DataTable table, int id, string name, string city)
      {
         DataRow newrow = table.NewRow();
         newrow["StudentID"] = id;
         newrow["StudentName"] = name;
         newrow["StudentCity"] = city;
         table.Rows.Add(newrow);
      }
   }
}

When you execute the program, observe the following:

The application first creates a data set and binds it with the grid view control using the DataBind() method of the GridView control.
The Createdataset() method is a user defined function, which creates a new DataSet object and then calls another user defined method CreateStudentTable() to create the table and add it to the Tables collection of the data set.
The CreateStudentTable() method calls the user defined methods AddNewColumn() and AddNewRow() to create the columns and rows of the table as well as to add data to the rows.

When the page is executed, it returns the rows of the table as shown:

ADO.Net Result

File Uploading

ASP.NET has two controls that allow users to upload files to the web server. Once the server receives the posted file data, the application can save it, check it, or ignore it. The following controls allow the file uploading:

HtmlInputFile - an HTML server control
FileUpload - and ASP.NET web control

Both controls allow file uploading, but the FileUpload control automatically sets the encoding of the form, whereas the HtmlInputFile does not do so.

In this tutorial, we use the FileUpload control. The FileUpload control allows the user to browse for and select the file to be uploaded, providing a browse button and a text box for entering the filename.

Once, the user has entered the filename in the text box by typing the name or browsing, the SaveAs method of the FileUpload control can be called to save the file to the disk.

The basic syntax of FileUpload is:

<asp:FileUpload ID= "Uploader" runat = "server" />

The FileUpload class is derived from the WebControl class, and inherits all its members. Apart from those, the FileUpload class has the following read-only properties:

Properties	Description
FileBytes	Returns an array of the bytes in a file to be uploaded.
FileContent	Returns the stream object pointing to the file to be uploaded.
FileName	Returns the name of the file to be uploaded.
HasFile	Specifies whether the control has a file to upload.
PostedFile	Returns a reference to the uploaded file.

The posted file is encapsulated in an object of type HttpPostedFile, which could be accessed through the PostedFile property of the FileUpload class.

The HttpPostedFile class has the following frequently used properties:

Properties	Description
ContentLength	Returns the size of the uploaded file in bytes.
ContentType	Returns the MIME type of the uploaded file.
FileName	Returns the full filename.
InputStream	Returns a stream object pointing to the uploaded file.

Example

The following example demonstrates the FileUpload control and its properties. The form has a FileUpload control along with a save button and a label control for displaying the file name, file type, and file length.

In the design view, the form looks as follows:

File Upload

The content file code is as given:

<body>
   <form id="form1" runat="server">
   
      <div>
         <h3> File Upload:</h3>
         <br />
         <asp:FileUpload ID="FileUpload1" runat="server" />
         <br /><br />
         <asp:Button ID="btnsave" runat="server" onclick="btnsave_Click"  Text="Save" style="width:85px" />
         <br /><br />
         <asp:Label ID="lblmessage" runat="server" />
      </div>
      
   </form>
</body>

The code behind the save button is as given:

protected void btnsave_Click(object sender, EventArgs e)
{
   StringBuilder sb = new StringBuilder();
   
   if (FileUpload1.HasFile)
   {
      try
      {
         sb.AppendFormat(" Uploading file: {0}", FileUpload1.FileName);
         
         //saving the file
         FileUpload1.SaveAs("<c:\\SaveDirectory>" + FileUpload1.FileName);
      
         //Showing the file information
         sb.AppendFormat("<br/> Save As: {0}",  FileUpload1.PostedFile.FileName);
         sb.AppendFormat("<br/> File type: {0}",    FileUpload1.PostedFile.ContentType);
         sb.AppendFormat("<br/> File length: {0}",  FileUpload1.PostedFile.ContentLength);
         sb.AppendFormat("<br/> File name: {0}",  FileUpload1.PostedFile.FileName);
         
      }catch (Exception ex)
      {
         sb.Append("<br/> Error <br/>");
         sb.AppendFormat("Unable to save file <br/> {0}", ex.Message);
      }
   }
   else
   {
      lblmessage.Text = sb.ToString();
   }
}

Note the following:

The StringBuilder class is derived from System.IO namespace, so it needs to be included.
The try and catch blocks are used for catching errors, and display the error message.

Ad Rotator

The AdRotator control randomly selects banner graphics from a list, which is specified in an external XML schedule file. This external XML schedule file is called the advertisement file.

The AdRotator control allows you to specify the advertisement file and the type of window that the link should follow in the AdvertisementFile and the Target property respectively.

The basic syntax of adding an AdRotator is as follows:

<asp:AdRotator  runat = "server" AdvertisementFile = "adfile.xml"  Target =  "_blank" />

Before going into the details of the AdRotator control and its properties, let us look into the construction of the advertisement file.

The Advertisement File

The advertisement file is an XML file, which contains the information about the advertisements to be displayed.

Extensible Markup Language (XML) is a W3C standard for text document markup. It is a text-based markup language that enables you to store data in a structured format by using meaningful tags. The term 'extensible' implies that you can extend your ability to describe a document by defining meaningful tags for the application.

XML is not a language in itself, like HTML, but a set of rules for creating new markup languages. It is a meta-markup language. It allows developers to create custom tag sets for special uses. It structures, stores, and transports the information.

Following is an example of XML file:

<BOOK>
   <NAME> Learn XML </NAME>
   <AUTHOR> Samuel Peterson </AUTHOR>
   <PUBLISHER> NSS Publications </PUBLISHER>
   <PRICE> $30.00</PRICE>
</BOOK>

Like all XML files, the advertisement file needs to be a structured text file with well-defined tags delineating the data. There are the following standard XML elements that are commonly used in the advertisement file:

Element	Description
Advertisements	Encloses the advertisement file.
Ad	Delineates separate ad.
ImageUrl	The path of image that will be displayed.
NavigateUrl	The link that will be followed when the user clicks the ad.
AlternateText	The text that will be displayed instead of the picture if it cannot be displayed.
Keyword	Keyword identifying a group of advertisements. This is used for filtering.
Impressions	The number indicating how often an advertisement will appear.
Height	Height of the image to be displayed.
Width	Width of the image to be displayed.

Apart from these tags, customs tags with custom attributes could also be included. The following code illustrates an advertisement file ads.xml:

<Advertisements>
   <Ad>
      <ImageUrl>rose1.jpg</ImageUrl>
      <NavigateUrl>http://www.1800flowers.com</NavigateUrl>
      <AlternateText>
         Order flowers, roses, gifts and more
      </AlternateText>
      <Impressions>20</Impressions>
      <Keyword>flowers</Keyword>
   </Ad>

   <Ad>
      <ImageUrl>rose2.jpg</ImageUrl>
      <NavigateUrl>http://www.babybouquets.com.au</NavigateUrl>
      <AlternateText>Order roses and flowers</AlternateText>
      <Impressions>20</Impressions>
      <Keyword>gifts</Keyword>
   </Ad>

   <Ad>
      <ImageUrl>rose3.jpg</ImageUrl>
      <NavigateUrl>http://www.flowers2moscow.com</NavigateUrl>
      <AlternateText>Send flowers to Russia</AlternateText>
      <Impressions>20</Impressions>
      <Keyword>russia</Keyword>
   </Ad>

   <Ad>
      <ImageUrl>rose4.jpg</ImageUrl>
      <NavigateUrl>http://www.edibleblooms.com</NavigateUrl>
      <AlternateText>Edible Blooms</AlternateText>
      <Impressions>20</Impressions>
      <Keyword>gifts</Keyword>
   </Ad>
</Advertisements>

Properties and Events of the AdRotator Class

The AdRotator class is derived from the WebControl class and inherits its properties. Apart from those, the AdRotator class has the following properties:

Properties	Description
AdvertisementFile	The path to the advertisement file.
AlternateTextFeild	The element name of the field where alternate text is provided. The default value is AlternateText.
DataMember	The name of the specific list of data to be bound when advertisement file is not used.
DataSource	Control from where it would retrieve data.
DataSourceID	Id of the control from where it would retrieve data.
Font	Specifies the font properties associated with the advertisement banner control.
ImageUrlField	The element name of the field where the URL for the image is provided. The default value is ImageUrl.
KeywordFilter	For displaying the keyword based ads only.
NavigateUrlField	The element name of the field where the URL to navigate to is provided. The default value is NavigateUrl.
Target	The browser window or frame that displays the content of the page linked.
UniqueID	Obtains the unique, hierarchically qualified identifier for the AdRotator control.

Following are the important events of the AdRotator class:

Events	Description
AdCreated	It is raised once per round trip to the server after creation of the control, but before the page is rendered
DataBinding	Occurs when the server control binds to a data source.
DataBound	Occurs after the server control binds to a data source.
Disposed	Occurs when a server control is released from memory, which is the last stage of the server control lifecycle when an ASP.NET page is requested
Init	Occurs when the server control is initialized, which is the first step in its lifecycle.
Load	Occurs when the server control is loaded into the Page object.
PreRender	Occurs after the Control object is loaded but prior to rendering.
Unload	Occurs when the server control is unloaded from memory.

Working with AdRotator Control

Create a new web page and place an AdRotator control on it.

<form id="form1" runat="server">
   <div>
      <asp:AdRotator ID="AdRotator1" runat="server" AdvertisementFile  ="~/ads.xml" onadcreated="AdRotator1_AdCreated" />
   </div>
</form>

The ads.xml file and the image files should be located in the root directory of the web site.

Try to execute the above application and observe that each time the page is reloaded, the ad is changed.

Clanders

The calendar control is a functionally rich web control, which provides the following capabilities:

Displaying one month at a time
Selecting a day, a week or a month
Selecting a range of days
Moving from month to month
Controlling the display of the days programmatically

The basic syntax of a calendar control is:

<asp:Calender ID = "Calendar1" runat = "server">
</asp:Calender>

Properties and Events of the Calendar Control

The calendar control has many properties and events, using which you can customize the actions and display of the control. The following table provides some important properties of the Calendar control:

Properties	Description
Caption	Gets or sets the caption for the calendar control.
CaptionAlign	Gets or sets the alignment for the caption.
CellPadding	Gets or sets the number of spaces between the data and the cell border.
CellSpacing	Gets or sets the space between cells.
DayHeaderStyle	Gets the style properties for the section that displays the day of the week.
DayNameFormat	Gets or sets format of days of the week.
DayStyle	Gets the style properties for the days in the displayed month.
FirstDayOfWeek	Gets or sets the day of week to display in the first column.
NextMonthText	Gets or sets the text for next month navigation control. The default value is >.
NextPrevFormat	Gets or sets the format of the next and previous month navigation control.
OtherMonthDayStyle	Gets the style properties for the days on the Calendar control that are not in the displayed month.
PrevMonthText	Gets or sets the text for previous month navigation control. The default value is <.
SelectedDate	Gets or sets the selected date.
SelectedDates	Gets a collection of DateTime objects representing the selected dates.
SelectedDayStyle	Gets the style properties for the selected dates.
SelectionMode	Gets or sets the selection mode that specifies whether the user can select a single day, a week or an entire month.
SelectMonthText	Gets or sets the text for the month selection element in the selector column.
SelectorStyle	Gets the style properties for the week and month selector column.
SelectWeekText	Gets or sets the text displayed for the week selection element in the selector column.
ShowDayHeader	Gets or sets the value indicating whether the heading for the days of the week is displayed.
ShowGridLines	Gets or sets the value indicating whether the gridlines would be shown.
ShowNextPrevMonth	Gets or sets a value indicating whether next and previous month navigation elements are shown in the title section.
ShowTitle	Gets or sets a value indicating whether the title section is displayed.
TitleFormat	Gets or sets the format for the title section.
Titlestyle	Get the style properties of the title heading for the Calendar control.
TodayDayStyle	Gets the style properties for today's date on the Calendar control.
TodaysDate	Gets or sets the value for today's date.
UseAccessibleHeader	Gets or sets a value that indicates whether to render the table header <th> HTML element for the day headers instead of the table data <td> HTML element.
VisibleDate	Gets or sets the date that specifies the month to display.
WeekendDayStyle	Gets the style properties for the weekend dates on the Calendar control.

The Calendar control has the following three most important events that allow the developers to program the calendar control. They are:

Events	Description
SelectionChanged	It is raised when a day, a week or an entire month is selected.
DayRender	It is raised when each data cell of the calendar control is rendered.
VisibleMonthChanged	It is raised when user changes a month.

Working with the Calendar Control

Putting a bare-bone calendar control without any code behind file provides a workable calendar to a site, which shows the months and days of the year. It also allows navigation to next and previous months.

Calendar controls allow the users to select a single day, a week, or an entire month. This is done by using the SelectionMode property. This property has the following values:

Properties	Description
Day	To select a single day.
DayWeek	To select a single day or an entire week.
DayWeekMonth	To select a single day, a week, or an entire month.
None	Nothing can be selected.

The syntax for selecting days:

<asp:Calender ID = "Calendar1" runat = "server" SelectionMode="DayWeekMonth">
</asp:Calender>

When the selection mode is set to the value DayWeekMonth, an extra column with the > symbol appears for selecting the week, and a >> symbol appears to the left of the days name for selecting the month.

Calendar2

Example

The following example demonstrates selecting a date and displays the date in a label:

The content file code is as follows:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="calendardemo._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
      
         <div>
            <h3> Your Birthday:</h3>
            <asp:Calendar ID="Calendar1" runat="server  SelectionMode="DayWeekMonth" onselectionchanged="Calendar1_SelectionChanged">
            </asp:Calendar>
         </div>
         
         <p>Todays date is: 
            <asp:Label ID="lblday" runat="server"></asp:Label>
         </p>
         
         <p>Your Birday is: 
            <asp:Label ID="lblbday" runat="server"></asp:Label>
         </p>
         
      </form>
   </body>
</html>

The event handler for the event SelectionChanged:

protected void Calendar1_SelectionChanged(object sender, EventArgs e)
{
   lblday.Text = Calendar1.TodaysDate.ToShortDateString();
   lblbday.Text = Calendar1.SelectedDate.ToShortDateString();
}

When the file is run, it should produce the following output:

Calendar3

Multi Views

MultiView and View controls allow you to divide the content of a page into different groups, displaying only one group at a time. Each View control manages one group of content and all the View controls are held together in a MultiView control.

The MultiView control is responsible for displaying one View control at a time. The View displayed is called the active view.

The syntax of MultiView control is:

<asp:MultView ID= "MultiView1" runat= "server">
</asp:MultiView>

The syntax of View control is:

<asp:View ID= "View1" runat= "server">
</asp:View>

However, the View control cannot exist on its own. It would render error if you try to use it stand-alone. It is always used with a Multiview control as:

<asp:MultView ID= "MultiView1" runat= "server">
   <asp:View ID= "View1" runat= "server"> </asp:View>
</asp:MultiView>

Properties of View and MultiView Controls

Both View and MultiView controls are derived from Control class and inherit all its properties, methods, and events. The most important property of the View control is Visible property of type Boolean, which sets the visibility of a view.

The MultiView control has the following important properties:

Properties	Description
Views	Collection of View controls within the MultiView.
ActiveViewIndex	A zero based index that denotes the active view. If no view is active, then the index is -1.

The CommandName attribute of the button control associated with the navigation of the MultiView control are associated with some related field of the MultiView control.

For example, if a button control with CommandName value as NextView is associated with the navigation of the multiview, it automatically navigates to the next view when the button is clicked.

The following table shows the default command names of the above properties:

Properties	Description
NextViewCommandName	NextView
PreviousViewCommandName	PrevView
SwitchViewByIDCommandName	SwitchViewByID
SwitchViewByIndexCommandName	SwitchViewByIndex

The important methods of the multiview control are:

Methods	Description
SetActiveview	Sets the active view
GetActiveview	Retrieves the active view

Every time a view is changed, the page is posted back to the server and a number of events are raised. Some important events are:

Events	Description
ActiveViewChanged	Raised when a view is changed
Activate	Raised by the active view
Deactivate	Raised by the inactive view

Apart from the above mentioned properties, methods and events, multiview control inherits the members of the control and object class.

Example

The example page has three views. Each view has two button for navigating through the views.

The content file code is as follows:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="multiviewdemo._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>
         Untitled Page
      </title>
   </head>
   
   <body>
      <form id="form1" runat="server">
      
         <div>
            <h2>MultiView and View Controls</h2>
            
            <asp:DropDownList ID="DropDownList1" runat="server" onselectedindexchanged="DropDownList1_SelectedIndexChanged">
            </asp:DropDownList>
            
            <hr />
            
            <asp:MultiView ID="MultiView1" runat="server" ActiveViewIndex="2"  onactiveviewchanged="MultiView1_ActiveViewChanged" >
               <asp:View ID="View1" runat="server">
                  <h3>This is view 1</h3>
                  <br />
                  <asp:Button CommandName="NextView" ID="btnnext1" runat="server" Text = "Go To Next" />
                  <asp:Button CommandArgument="View3" CommandName="SwitchViewByID" ID="btnlast" runat="server" Text  ="Go To Last" />
               </asp:View> 
					
               <asp:View ID="View2" runat="server">
                  <h3>This is view 2</h3>
                  <asp:Button CommandName="NextView" ID="btnnext2" runat="server" Text = "Go To Next" />
                  <asp:Button CommandName="PrevView" ID="btnprevious2" runat="server" Text = "Go To Previous View" />
               </asp:View> 

               <asp:View ID="View3" runat="server">
                  <h3> This is view 3</h3>
                  <br />
                  <asp:Calendar ID="Calender1" runat="server"></asp:Calendar>
                  <br />
                  <asp:Button  CommandArgument="0" CommandName="SwitchViewByIndex" ID="btnfirst"   runat="server" Text = "Go To Next" />
                  <asp:Button CommandName="PrevView" ID="btnprevious" runat="server" Text = "Go To Previous View" />
               </asp:View> 
               
            </asp:MultiView>
         </div>
         
      </form>
   </body>
</html>

Observe the following:

The MultiView.ActiveViewIndex determines which view will be shown. This is the only view rendered on the page. The default value for the ActiveViewIndex is -1, when no view is shown. Since the ActiveViewIndex is defined as 2 in the example, it shows the third view, when executed.

MultiView

Panel Controls

The Panel control works as a container for other controls on the page. It controls the appearance and visibility of the controls it contains. It also allows generating controls programmatically.

The basic syntax of panel control is as follows:

<asp:Panel ID= "Panel1"  runat = "server">
</asp:Panel>

The Panel control is derived from the WebControl class. Hence it inherits all the properties, methods and events of the same. It does not have any method or event of its own. However it has the following properties of its own:

Properties	Description
BackImageUrl	URL of the background image of the panel.
DefaultButton	Gets or sets the identifier for the default button that is contained in the Panel control.
Direction	Text direction in the panel.
GroupingText	Allows grouping of text as a field.
HorizontalAlign	Horizontal alignment of the content in the panel.
ScrollBars	Specifies visibility and location of scrollbars within the panel.
Wrap	Allows text wrapping.

Working with the Panel Control

Let us start with a simple scrollable panel of specific height and width and a border style. The ScrollBars property is set to both the scrollbars, hence both the scrollbars are rendered.

The source file has the following code for the panel tag:

<asp:Panel ID="Panel1" runat="server" BorderColor="#990000" BorderStyle="Solid" 
   Borderstyle="width:1px" Height="116px" ScrollBars="Both" style="width:278px">
   
   This is a scrollable panel.
   <br />
   <br />

   <asp:Button ID="btnpanel" runat="server" Text="Button" style="width:82px" />
</asp:Panel>

The panel is rendered as follows:

Panel

Example

The following example demonstrates dynamic content generation. The user provides the number of label controls and textboxes to be generated on the panel. The controls are generated programmatically.

Change the properties of the panel using the properties window. When you select a control on the design view, the properties window displays the properties of that particular control and allows you to make changes without typing.

Panel2

The source file for the example is as follows:

<form id="form1" runat="server">
   <div>
      <asp:Panel ID="pnldynamic" runat="server" BorderColor="#990000" 
         BorderStyle="Solid" Borderstyle="width:1px" Height="150px"  ScrollBars="Auto" style="width:60%" BackColor="#CCCCFF"  Font-Names="Courier" HorizontalAlign="Center">
     
         This panel shows dynamic control generation:
         <br />
         <br />
      </asp:Panel>
   </div>

   <table style="width: 51%;">
      <tr>
         <td class="style2">No of Labels:</td>
         <td class="style1">
            <asp:DropDownList ID="ddllabels" runat="server">
               <asp:ListItem>0</asp:ListItem>
               <asp:ListItem>1</asp:ListItem>
               <asp:ListItem>2</asp:ListItem>
               <asp:ListItem>3</asp:ListItem>
               <asp:ListItem>4</asp:ListItem>
            </asp:DropDownList>
         </td>
      </tr>

      <tr>
         <td class="style2"> </td>
         <td class="style1"> </td>
      </tr>

      <tr>
         <td class="style2">No of Text Boxes :</td>
         <td class="style1">
            <asp:DropDownList ID="ddltextbox" runat="server">
               <asp:ListItem>0</asp:ListItem>
               <asp:ListItem Value="1"></asp:ListItem>
               <asp:ListItem>2</asp:ListItem>
               <asp:ListItem>3</asp:ListItem>
               <asp:ListItem Value="4"></asp:ListItem>
            </asp:DropDownList>
         </td>
      </tr>

      <tr>
         <td class="style2"> </td>
         <td class="style1"> </td>
      </tr>

      <tr>
         <td class="style2">
            <asp:CheckBox ID="chkvisible" runat="server" 
               Text="Make the Panel Visible" />
         </td>

         <td class="style1">
            <asp:Button ID="btnrefresh" runat="server" Text="Refresh Panel" 
               style="width:129px" />
         </td>
      </tr>
   </table>
</form>

The code behind the Page_Load event is responsible for generating the controls dynamically:

public partial class _Default : System.Web.UI.Page
{
   protected void Page_Load(object sender, EventArgs e)
   {
      //make the panel visible
      pnldynamic.Visible = chkvisible.Checked;

      //generating the lable controls:
      int n = Int32.Parse(ddllabels.SelectedItem.Value);
      for (int i = 1; i <= n; i++)
      {
         Label lbl = new Label();
         lbl.Text = "Label" + (i).ToString();
         pnldynamic.Controls.Add(lbl);
         pnldynamic.Controls.Add(new LiteralControl("<br />"));
      }
      
      //generating the text box controls:

      int m = Int32.Parse(ddltextbox.SelectedItem.Value);
      for (int i = 1; i <= m; i++)
      {
         TextBox txt = new TextBox();
         txt.Text = "Text Box" + (i).ToString();
         pnldynamic.Controls.Add(txt);
         pnldynamic.Controls.Add(new LiteralControl("<br />"));
      }
   }
}

When executed, the panel is rendered as:

Panel3

Data Sources

A data source control interacts with the data-bound controls and hides the complex data binding processes. These are the tools that provide data to the data bound controls and support execution of operations like insertions, deletions, sorting, and updates.

Each data source control wraps a particular data provider-relational databases, XML documents, or custom classes and helps in:

Managing connection
Selecting data
Managing presentation aspects like paging, caching, etc.
Manipulating data

There are many data source controls available in ASP.NET for accessing data from SQL Server, from ODBC or OLE DB servers, from XML files, and from business objects.

Based on type of data, these controls could be divided into two categories:

Hierarchical data source controls
Table-based data source controls

The data source controls used for hierarchical data are:

XMLDataSource - It allows binding to XML files and strings with or without schema information.
SiteMapDataSource - It allows binding to a provider that supplies site map information.

The data source controls used for tabular data are:

Data source controls	Description
SqlDataSource	It represents a connection to an ADO.NET data provider that returns SQL data, including data sources accessible via OLEDB and ODBC.
ObjectDataSource	It allows binding to a custom .Net business object that returns data.
LinqdataSource	It allows binding to the results of a Linq-to-SQL query (supported by ASP.NET 3.5 only).
AccessDataSource	It represents connection to a Microsoft Access database.

Data Source Views

Data source views are objects of the DataSourceView class. Which represent a customized view of data for different data operations such as sorting, filtering, etc.

The DataSourceView class serves as the base class for all data source view classes, which define the capabilities of data source controls.

The following table provides the properties of the DataSourceView class:

Properties	Description
CanDelete	Indicates whether deletion is allowed on the underlying data source.
CanInsert	Indicates whether insertion is allowed on the underlying data source.
CanPage	Indicates whether paging is allowed on the underlying data source.
CanRetrieveTotalRowCount	Indicates whether total row count information is available.
CanSort	Indicates whether the data could be sorted.
CanUpdate	Indicates whether updates are allowed on the underlying data source.
Events	Gets a list of event-handler delegates for the data source view.
Name	Name of the view.

The following table provides the methods of the DataSourceView class:

Methods	Description
CanExecute	Determines whether the specified command can be executed.
ExecuteCommand	Executes the specific command.
ExecuteDelete	Performs a delete operation on the list of data that the DataSourceView object represents.
ExecuteInsert	Performs an insert operation on the list of data that the DataSourceView object represents.
ExecuteSelect	Gets a list of data from the underlying data storage.
ExecuteUpdate	Performs an update operation on the list of data that the DataSourceView object represents.
Delete	Performs a delete operation on the data associated with the view.
Insert	Performs an insert operation on the data associated with the view.
Select	Returns the queried data.
Update	Performs an update operation on the data associated with the view.
OnDataSourceViewChanged	Raises the DataSourceViewChanged event.
RaiseUnsupportedCapabilitiesError	Called by the RaiseUnsupportedCapabilitiesError method to compare the capabilities requested for an ExecuteSelect operation against those that the view supports.

The SqlDataSource Control

The SqlDataSource control represents a connection to a relational database such as SQL Server or Oracle database, or data accessible through OLEDB or Open Database Connectivity (ODBC). Connection to data is made through two important properties ConnectionString and ProviderName.

The following code snippet provides the basic syntax of the control:

<asp:SqlDataSource runat="server" ID="MySqlSource"
   ProviderName='<%$ ConnectionStrings:LocalNWind.ProviderName  %>'
   ConnectionString='<%$ ConnectionStrings:LocalNWind %>'
   SelectionCommand= "SELECT * FROM EMPLOYEES" />

<asp:GridView ID="GridView1" runat="server" DataSourceID="MySqlSource" />

Configuring various data operations on the underlying data depends upon the various properties (property groups) of the data source control.

The following table provides the related sets of properties of the SqlDataSource control, which provides the programming interface of the control:

Property Group	Description
DeleteCommand, DeleteParameters, DeleteCommandType	Gets or sets the SQL statement, parameters, and type for deleting rows in the underlying data.
FilterExpression, FilterParameters	Gets or sets the data filtering string and parameters.
InsertCommand, InsertParameters, InsertCommandType	Gets or sets the SQL statement, parameters, and type for inserting rows in the underlying database.
SelectCommand, SelectParameters, SelectCommandType	Gets or sets the SQL statement, parameters, and type for retrieving rows from the underlying database.
SortParameterName	Gets or sets the name of an input parameter that the command's stored procedure will use to sort data.
UpdateCommand, UpdateParameters, UpdateCommandType	Gets or sets the SQL statement, parameters, and type for updating rows in the underlying data store.

The following code snippet shows a data source control enabled for data manipulation:

<asp:SqlDataSource runat="server" ID= "MySqlSource"
   ProviderName='<%$ ConnectionStrings:LocalNWind.ProviderName  %>'
   ConnectionString=' <%$ ConnectionStrings:LocalNWind %>'
   SelectCommand= "SELECT * FROM EMPLOYEES"
   UpdateCommand= "UPDATE EMPLOYEES SET LASTNAME=@lame"
   DeleteCommand= "DELETE FROM EMPLOYEES WHERE EMPLOYEEID=@eid"
   FilterExpression= "EMPLOYEEID > 10">
   .....
   .....
</asp:SqlDataSource>

The ObjectDataSource Control

The ObjectDataSource Control enables user-defined classes to associate the output of their methods to data bound controls. The programming interface of this class is almost same as the SqlDataSource control.

Following are two important aspects of binding business objects:

The bindable class should have a default constructor, it should be stateless, and have methods that can be mapped to select, update, insert, and delete semantics.
The object must update one item at a time, batch operations are not supported.

Let us go directly to an example to work with this control. The student class is the class to be used with an object data source. This class has three properties: a student id, name, and city. It has a default constructor and a GetStudents method for retrieving data.

The student class:

public class Student
{
   public int StudentID { get; set; }
   public string Name { get; set; }
   public string City { get; set; }
   
   public Student()
   { }
   
   public DataSet GetStudents()
   {
      DataSet ds = new DataSet();
      DataTable dt = new DataTable("Students");
      
      dt.Columns.Add("StudentID", typeof(System.Int32));
      dt.Columns.Add("StudentName", typeof(System.String));
      dt.Columns.Add("StudentCity", typeof(System.String));
      dt.Rows.Add(new object[] { 1, "M. H. Kabir", "Calcutta" });
      dt.Rows.Add(new object[] { 2, "Ayan J. Sarkar", "Calcutta" });
      ds.Tables.Add(dt);
      
      return ds;
   }
}

Take the following steps to bind the object with an object data source and retrieve data:

Create a new web site.
Add a class (Students.cs) to it by right clicking the project from the Solution Explorer, adding a class template, and placing the above code in it.
Build the solution so that the application can use the reference to the class.
Place an object data source control in the web form.
Configure the data source by selecting the object.

selecting the object

Select a data method(s) for different operations on data. In this example, there is only one method.

Select a data method

Place a data bound control such as grid view on the page and select the object data source as its underlying data source.

Data Bound Control

At this stage, the design view should look like the following:

Object Data Source

Run the project, it retrieves the hard coded tuples from the students class.

Object Data Result

The AccessDataSource Control

The AccessDataSource control represents a connection to an Access database. It is based on the SqlDataSource control and provides simpler programming interface. The following code snippet provides the basic syntax for the data source:

<asp:AccessDataSource ID="AccessDataSource1 runat="server" 
   DataFile="~/App_Data/ASPDotNetStepByStep.mdb" SelectCommand="SELECT * FROM  [DotNetReferences]">
</asp:AccessDataSource>

The AccessDataSource control opens the database in read-only mode. However, it can also be used for performing insert, update, or delete operations. This is done using the ADO.NET commands and parameter collection.

Updates are problematic for Access databases from within an ASP.NET application because an Access database is a plain file and the default account of the ASP.NET application might not have the permission to write to the database file.

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ASP.NET (Part-3)

Managing State

View State

Example

Control State

Session State

Example

Application State

Validators

BaseValidator Class

RequiredFieldValidator Control

RangeValidator Control

CompareValidator Control

RegularExpressionValidator

CustomValidator

ValidationSummary

Validation Groups

Example

Database Access

Retrieve and display data

ADO.net

The DataSet Class

The DataTable Class

The DataRow Class

The DataAdapter Object

The DataReader Object

DbCommand and DbConnection Objects

Example

File Uploading

Example

Ad Rotator

The Advertisement File

Properties and Events of the AdRotator Class

Working with AdRotator Control

Clanders

Properties and Events of the Calendar Control

Working with the Calendar Control

Example

Multi Views

Properties of View and MultiView Controls

Example

Panel Controls

Working with the Panel Control

Example

Data Sources

Data Source Views

The SqlDataSource Control

The ObjectDataSource Control

The AccessDataSource Control

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