CheckBox.CheckedChanged Event (System.Web.UI.WebControls)

CheckedChanged Event

.NET Framework Class Library

CheckBox..::.CheckedChanged Event

Occurs when the value of the Checked property changes between posts to the server.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in System.Web.dll)

Syntax

Visual Basic (Declaration)

Public Event CheckedChanged As EventHandler

Visual Basic (Usage)

Dim instance As CheckBox
Dim handler As EventHandler

AddHandler instance.CheckedChanged, handler

public event EventHandler CheckedChanged

Visual C++

public:
virtual  event EventHandler^ CheckedChanged {
    void add (EventHandler^ value);
    void remove (EventHandler^ value);
}

JScript

JScript does not support events.

ASP.NET

<asp:CheckBox OnCheckedChanged="EventHandler" />

Implements

ICheckBoxControl..::.CheckedChanged

Remarks

The CheckedChanged event is raised when the value of the Checked property changes between posts to the server. This event does not post the page back to the server unless the AutoPostBack property is set to true.

Note:
A CheckBox control must persist some values between posts to the server for this event to work correctly. Be sure that view state is enabled for this control.

For more information about handling events, see How to: Consume Events in a Web Forms Application.

Topic	Location
How to: Respond to User Selection in a CheckBox Web Server Control	Building ASP .NET Web Applications
How to: Respond to User Selection in a CheckBox Web Server Control	Building ASP .NET Web Applications
How to: Respond to User Selection in a CheckBox Web Server Control	Building ASP .NET Web Applications in Visual Studio
How to: Respond to User Selection in a CheckBox Web Server Control	Building ASP .NET Web Applications in Visual Studio
How to: Set and Get the Selection in a RadioButton Web Server Control	Building ASP .NET Web Applications
How to: Set and Get the Selection in a RadioButton Web Server Control	Building ASP .NET Web Applications
How to: Set and Get the Selection in a RadioButton Web Server Control	Building ASP .NET Web Applications in Visual Studio
How to: Set and Get the Selection in a RadioButton Web Server Control	Building ASP .NET Web Applications in Visual Studio
Walkthrough: Validating User Input in a Web Forms Page	Building ASP .NET Web Applications in Visual Studio
Walkthrough: Validating User Input in a Web Forms Page	Building Applications with Visual Web Developer
Walkthrough: Validating User Input in a Web Forms Page	Building ASP .NET Web Applications in Visual Studio

Examples

The following example demonstrates how to specify and code the handler for the CheckedChanged event of a CheckBox control.

Note:
The following code samples use the single-file code model and may not work correctly if copied directly into a code-behind file. Each code sample must be copied into an empty text file that has an .aspx extension. For more information on the Web Forms code model, see ASP.NET Web Page Code Model.

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head runat="server">
    <title>CheckBox CheckedChanged Example</title>
<script runat="server">

      Sub Check_Clicked(sender As Object, e As EventArgs) 

         ' Calculate the subtotal and display the result in currency format.
         ' Include tax if the check box is selected.
         Message.Text = CalculateTotal(checkbox1.Checked).ToString("c")

      End Sub

      Sub Page_Load(sender As Object, e As EventArgs)

         ' Display the subtotal without tax when the page is first loaded.
         If Not IsPostBack Then

            ' Calculate the subtotal and display the result in currency format.
            Message.Text = CalculateTotal(false).ToString("c")

         End If

      End Sub

      Function CalculateTotal(Taxable As Boolean) As Double 

         ' Calculate the subtotal for the example.
         Dim Result As Double = 1.99 + 2.99 + 3.99

         ' Add tax, if applicable.
         If(Taxable)

            Result += Result * 0.086

         End If

         Return Result 

      End Function

   </script>

</head>

<body>

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

      <h3>CheckBox CheckedChanged Example</h3>

      Select whether to include tax in the subtotal.

      <br /><br />

      <table border="1" cellpadding="5">

         <tr>

            <th colspan="2">

               Shopping cart

            </th>

         </tr>

         <tr>

            <td>

               Item 1

            </td>

            <td>

               $1.99

            </td>

         </tr>

         <tr>

            <td>

               Item 2

            </td>

            <td>

               $2.99

            </td>

         </tr>

         <tr>

            <td>

               Item 3

            </td>

            <td>

               $3.99

            </td>

         </tr>

         <tr>

            <td>

               <b>Subtotal</b>

            </td>

            <td>

               <asp:Label id="Message" runat="server"/>

            </td>

         </tr>

         <tr>

            <td colspan="2">

               <asp:CheckBox id="checkbox1" runat="server"
                    AutoPostBack="True"
                    Text="Include 8.6% sales tax"
                    TextAlign="Right"
                    OnCheckedChanged="Check_Clicked"/>

            </td>

         </tr>

      </table>

   </form>

</body>

</html>

<%@ Page Language="C#" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head runat="server">
    <title>CheckBox CheckedChanged Example</title>
<script runat="server">

      void Check_Clicked(Object sender, EventArgs e) 
      {

         // Calculate the subtotal and display the result in currency format.
         // Include tax if the check box is selected.
         Message.Text = CalculateTotal(checkbox1.Checked).ToString("c");

      }

      void Page_Load(Object sender, EventArgs e)
      {

         // Display the subtotal without tax when the page is first loaded.
         if(!IsPostBack)
         {

            // Calculate the subtotal and display the result in currency format.
            Message.Text = CalculateTotal(false).ToString("c");

         }

      }

      double CalculateTotal(bool Taxable)
      {

         // Calculate the subtotal for the example.
         double Result = 1.99 + 2.99 + 3.99;

         // Add tax, if applicable.
         if(Taxable)
         {
            Result += Result * 0.086;
         }

         return Result; 

      }

   </script>

</head>

<body>

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

      <h3>CheckBox CheckedChanged Example</h3>

      Select whether to include tax in the subtotal.

      <br /><br />

      <table border="1" cellpadding="5">

         <tr>

            <th colspan="2">

               Shopping cart

            </th>

         </tr>

         <tr>

            <td>

               Item 1

            </td>

            <td>

               $1.99

            </td>

         </tr>

         <tr>

            <td>

               Item 2

            </td>

            <td>

               $2.99

            </td>

         </tr>

         <tr>

            <td>

               Item 3

            </td>

            <td>

               $3.99

            </td>

         </tr>

         <tr>

            <td>

               <b>Subtotal</b>

            </td>

            <td>

               <asp:Label id="Message" runat="server"/>

            </td>

         </tr>

         <tr>

            <td colspan="2">

               <asp:CheckBox id="checkbox1" runat="server"
                    AutoPostBack="True"
                    Text="Include 8.6% sales tax"
                    TextAlign="Right"
                    OnCheckedChanged="Check_Clicked"/>

            </td>

         </tr>

      </table>

   </form>

</body>

</html>

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head runat="server">
    <title>CheckBox CheckedChanged Example</title>
<script runat="server">

      Sub Check_Clicked(sender As Object, e As EventArgs) 

         ' Calculate the subtotal and display the result in currency format.
         ' Include tax if the check box is selected.
         Message.Text = CalculateTotal(checkbox1.Checked).ToString("c")

      End Sub

      Sub Page_Load(sender As Object, e As EventArgs)

         ' Display the subtotal without tax when the page is first loaded.
         If Not IsPostBack Then

            ' Calculate the subtotal and display the result in 
            ' currency format.
            Message.Text = CalculateTotal(false).ToString("c")

         End If

         ' Manually register the event-handling method for the   
         ' CheckedChanged event of the CheckBox control.
         AddHandler checkbox1.CheckedChanged, AddressOf Check_Clicked

      End Sub

      Function CalculateTotal(Taxable As Boolean) As Double 

         ' Calculate the subtotal for the example.
         Dim Result As Double = 1.99 + 2.99 + 3.99

         ' Add tax, if applicable.
         If(Taxable)

            Result += Result * 0.086

         End If

         Return Result 

      End Function

   </script>

</head>

<body>

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

      <h3>CheckBox CheckedChanged Example</h3>

      Select whether to include tax in the subtotal.

      <br /><br />

      <table border="1" cellpadding="5">

         <tr>

            <th colspan="2">

               Shopping cart

            </th>

         </tr>

         <tr>

            <td>

               Item 1

            </td>

            <td>

               $1.99

            </td>

         </tr>

         <tr>

            <td>

               Item 2

            </td>

            <td>

               $2.99

            </td>

         </tr>

         <tr>

            <td>

               Item 3

            </td>

            <td>

               $3.99

            </td>

         </tr>

         <tr>

            <td>

               <b>Subtotal</b>

            </td>

            <td>

               <asp:Label id="Message" runat="server"/>

            </td>

         </tr>

         <tr>

            <td colspan="2">

               <asp:CheckBox id="checkbox1" runat="server"
                    AutoPostBack="True"
                    Text="Include 8.6% sales tax"
                    TextAlign="Right"
                    OnCheckedChanged="Check_Clicked"/>

            </td>

         </tr>

      </table>

   </form>

</body>

</html>

<%@ Page Language="C#" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head runat="server">
    <title>CheckBox CheckedChanged Example</title>
<script runat="server">

      void Check_Clicked(Object sender, EventArgs e) 
      {

         // Calculate the subtotal and display the result in currency format.
         // Include tax if the check box is selected.
         Message.Text = CalculateTotal(checkbox1.Checked).ToString("c");

      }

      void Page_Load(Object sender, EventArgs e)
      {

         // Display the subtotal without tax when the page is first loaded.
         if(!IsPostBack)
         {

            // Calculate the subtotal and display the result in 
            // currency format.
            Message.Text = CalculateTotal(false).ToString("c");

         }

         // Manually register the event-handling method for the   
         // CheckedChanged event of the CheckBox control.
         checkbox1.CheckedChanged += new EventHandler(this.Check_Clicked);

      }

      double CalculateTotal(bool Taxable)
      {

         // Calculate the subtotal for the example.
         double Result = 1.99 + 2.99 + 3.99;

         // Add tax, if applicable.
         if(Taxable)
         {
            Result += Result * 0.086;
         }

         return Result; 

      }

   </script>

</head>

<body>

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

      <h3>CheckBox CheckedChanged Example</h3>

      Select whether to include tax in the subtotal.

      <br /><br />

      <table border="1" cellpadding="5">

         <tr>

            <th colspan="2">

               Shopping cart

            </th>

         </tr>

         <tr>

            <td>

               Item 1

            </td>

            <td>

               $1.99

            </td>

         </tr>

         <tr>

            <td>

               Item 2

            </td>

            <td>

               $2.99

            </td>

         </tr>

         <tr>

            <td>

               Item 3

            </td>

            <td>

               $3.99

            </td>

         </tr>

         <tr>

            <td>

               <b>Subtotal</b>

            </td>

            <td>

               <asp:Label id="Message" runat="server"/>

            </td>

         </tr>

         <tr>

            <td colspan="2">

               <asp:CheckBox id="checkbox1" runat="server"
                    AutoPostBack="True"
                    Text="Include 8.6% sales tax"
                    TextAlign="Right"/>

            </td>

         </tr>

      </table>

   </form>

</body>

</html>

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Reference

CheckBox Class

CheckBox Members

System.Web.UI.WebControls Namespace

OnCheckedChanged

Other Resources

CheckBox and CheckBoxList Web Server Controls Overview

How to: Consume Events in a Web Forms Application