Event handler for dynamically added control does not work

Question

I am adding a dynamic control to my webpage using an update panel. I create an event handler for this dynamic control as well. So although the control is added to the webpage the event handler for this control doesn't work.

my c# code

protected void Button1_Click(object sender, EventArgs e)
{
    CheckBox cbTest = new CheckBox();
    cbTest.Text = "Click me for fun";
    cbTest.AutoPostBack = true; 
    cbTest.CheckedChanged+=new EventHandler(cbTest_CheckedChanged);
    UpdatePanel1.ContentTemplateContainer.Controls.Add(cbTest);
    DynamicPlaceHolder.Controls.Add(cbTest);
}
public void cbTest_CheckedChanged(object sender, EventArgs e)
{
    TextBox1.Text = "Yes. It worked!!!";
}

My Aspx code.

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <fieldset>
            <legend>UpdatePanel</legend>
            <asp:PlaceHolder ID="DynamicPlaceHolder" runat="server" ></asp:PlaceHolder>
            <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
        </fieldset>
    </ContentTemplate>
</asp:UpdatePanel>
<asp:TextBox Width="200px" runat="server" ID="TextBox1"></asp:TextBox>

What happens when i click the button is the check box is created. However when i check the check box the panel just refreshes and the text box is not updated with the text "Yes. It worked!!!".

Answer 1

First, why are you adding the CheckBox to UpdatePanel1.ContentTemplateContainer and even to DynamicPlaceHolder ?

So change it to this:

//UpdatePanel1.ContentTemplateContainer.Controls.Add(cbTest);
DynamicPlaceHolder.Controls.Add(cbTest);

You better assign events in the Page_Load :

protected void Page_Load(object sender, EventArgs e)
{
    for (int i = 0; i < DynamicPlaceHolder.Controls.Count; i++)
    {
        Control ctrl = DynamicPlaceHolder.Controls[i];
        if (ctrl is CheckBox)
        {
            CheckBox chk = (CheckBox)ctrl;
            chk.CheckedChanged += new EventHandler(cbTest_CheckedChanged);
        }
    }
}