title: Check/Uncheck All items in CheckBoxList in ASP.NET
body: <p>I have a CheckBoxList like following</p>
  
  <pre><code>protected void Page_Load(object sender, EventArgs e)
  {
      if (!IsPostBack)
      {
          CheckBoxList1.Items.Add(new ListItem("Check/Uncheck All","0"));
          CheckBoxList1.Items.Add(new ListItem("A","1"));
          CheckBoxList1.Items.Add(new ListItem("B","2"));
          CheckBoxList1.Items.Add(new ListItem("C", "3"));
          CheckBoxList1.Items.Add(new ListItem("D", "4"));
      }        
  }
  </code></pre>
  
  <p>I want whenever the first item is checked to check the rest of the items and whenever unchecked to uncheck the rest. Also the user can select every item separately.</p>
  
  <p>I want do this with code behind without JavaScript or JQuery.</p>