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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)

public event EventHandler CheckedChanged
<asp:CheckBox OnCheckedChanged="EventHandler" />

Implements

ICheckBoxControl.CheckedChanged

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.

NoteNote

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.

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

NoteNote

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 Forms Page Code Model.


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

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

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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