I have created a custom cofirm message box control and I created an event like this-

[Category("Action")]
[Description("Raised when the user clicks the button(ok)")]
    public event EventHandler Submit;

protected virtual void OnSubmit(EventArgs e) {
     if (Submit != null)
        Submit(this, e);
}

The Event OnSubmit occurs when user click the OK button on the Confrim Box.

void IPostBackEventHandler.RaisePostBackEvent(string eventArgument)
{
    OnSubmit(e);
}

Now I am adding this OnSubmit Event Dynamically like this-
In aspx-

<my:ConfirmMessageBox ID="cfmTest" runat="server" ></my:ConfirmMessageBox>
    <asp:Button ID="btnCallMsg" runat="server" onclick="btnCallMsg_Click" />
    <asp:TextBox ID="txtResult" runat="server" ></asp:TextBox>

In cs-

protected void btnCallMsg_Click(object sender, EventArgs e)
{
  cfmTest.Submit += cfmTest_Submit;//Dynamically Add Event
  cfmTest.ShowConfirm("Are you sure to Save Data?");  //Show Confirm Message using Custom Control Message Box
}

protected void cfmTest_Submit(object sender, EventArgs e)
    {
      txtResult.Text = "User Confirmed";//I set the text to "User Confrimed" but it's not displayed
      txtResult.Focus();//I focus the textbox but I got Error
    }

The Error I got is-
System.InvalidOperationException was unhandled by user code Message="SetFocus can only be called before and during PreRender." Source="System.Web"

So, when I dynamically add and fire custom control's event, there is an error in Web Control. If I add event in aspx file like this,

<my:ConfirmMessageBox ID="cfmTest" runat="server" OnSubmit="cfmTest_Submit"></my:ConfirmMessageBox>

There is no error and work fine.

Can anybody help me to add event dynamically to custom control?
Thanks.