ASP.NET Tutorial/ASP.net Controls/CheckBox

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asp: CheckBox changed event (C#)

File: Default.aspx
<%@ Page language="c#" Inherits="EventTracker" CodeFile="Default.aspx.cs" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
 "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
  <title>Event Tracker</title>
</head>
<body>
  <form id="Form1" runat="server">
    <div>       
      <h1>Controls being monitored for change events:</h1>
      <asp:TextBox ID="txt" 
                   runat="server" 
                   AutoPostBack="true"
                   OnTextChanged="CtrlChanged" />
      <br /><br />
      <asp:CheckBox ID="chk" 
                    runat="server" 
                    AutoPostBack="true"
                    OnCheckedChanged="CtrlChanged"/>
      <br /><br />
      <asp:RadioButton ID="opt1" runat="server" GroupName="Sample"
       AutoPostBack="true" OnCheckedChanged="CtrlChanged"/>
      <asp:RadioButton ID="opt2" runat="server" GroupName="Sample"
       AutoPostBack="true" OnCheckedChanged="CtrlChanged"/>
      <br /><br /><br /> 
       <h1>List of events:</h1>
      <asp:ListBox ID="lstEvents" runat="server" Width="355px"
       Height="305px" /><br />      
    </div>
  </form>
</body>
</html>

File: Default.aspx.cs
using System;
using System.Collections;
using System.ruponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

public partial class EventTracker : System.Web.UI.Page
{
  protected void Page_Load(object sender, System.EventArgs e)
  {
     Log("<< Page_Load >>");
  }
  private void Log(string entry)
  {
    lstEvents.Items.Add(entry);
    lstEvents.SelectedIndex = lstEvents.Items.Count - 1;
  }
  protected void Page_PreRender(object sender, System.EventArgs e)
  {
    Log("Page_PreRender");
  }
  protected void CtrlChanged(Object sender, EventArgs e)
  {
    string ctrlName = ((Control)sender).ID;
    Log(ctrlName + " Changed");
  }
}


Get selected CheckBox

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="CheckBox" %>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        What are your favorite ice cream flavors?<br />
        <br />
        <asp:CheckBox ID="A" runat="server" Text="A" /><br />
        <br />
        <asp:CheckBox ID="B" runat="server" Text="B" /><br />
        <br />
        <asp:CheckBox ID="C" runat="server" Text="C" /><br />
        <br />
        <asp:Button ID="btnSubmit" runat="server" Text="Click Me" /><br />
        <br />
        <asp:Label ID="results" runat="server"></asp:Label></div>
    </form>
</body>
</html>

File: Default.aspx.vb
Partial Class CheckBox
    Inherits System.Web.UI.Page
    Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
        results.Text = ""
        If A.Checked Then
            results.Text &= "A."
        End If
        If B.Checked Then
            results.Text &= "B."
        End If
        If C.Checked Then
            results.Text &= "C."
        End If
    End Sub
End Class


Import properties, events and methods of CheckBox control

AccessKey:      specify a key that navigates to the TextBox control.
AutoPostBack:   post the form containing the CheckBox back to the server automatically when the CheckBox is checked or unchecked.
Checked:        get or set whether the CheckBox is checked.
Enabled:        disable the TextBox.
TabIndex:       specify the tab order of the check box.
Text:           provide a label for the check box.
TextAlign:      align the label for the check box. Possible values are Left and Right.
Focus:          set the initial form focus to the check box.
CheckedChanged: Raised on the server when the check box is checked or unchecked.
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        lblResult.Text = chkNewsletter.Checked.ToString();
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show CheckBox</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:CheckBox
        id="chkNewsletter"
        Text="Receive Newsletter?"
        Runat="server" />
    <br />
    <asp:Button
        id="btnSubmit"
        Text="Submit"
        OnClick="btnSubmit_Click"
        Runat="server" />
    <hr />
    <asp:Label
        id="lblResult"
        Runat="server" />
    </div>
    </form>
</body>
</html>


use the AutoPostBack property to post the form to the server automatically when the check box is checked or unchecked.

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    protected void chkNewsletter_CheckedChanged(object sender, EventArgs e)
    {
        lblResult.Text = chkNewsletter.Checked.ToString();
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>CheckBox AutoPostBack</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:CheckBox
        id="chkNewsletter"
        Text="Receive Newsletter?"
        AutoPostBack="true"
        OnCheckedChanged="chkNewsletter_CheckedChanged"
        Runat="server" />
    <hr />
    <asp:Label
        id="lblResult"
        Runat="server" />
    </div>
    </form>
</body>
</html>
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ASP.net_Controls/CheckBox&oldid=3389»