I have a UserControl that contains contains a ModalPopupExtender.  I need to set TargetControlID to a control that will exist on the parent page of the UserControl.  Preferably I want this ID to exist as a property where the user can drop the control on the page and set the TargetControlID at design time.  For some reason, I am getting a null reference when I execute the code.  Here's a snippet of the code:

public partial class MyUserControl: System.Web.UI.UserControl
{

    private string _targetControlID;
    public string TargetControlID
    {
        get { return _targetControlID; }
        set { _targetControlID = value; }
    }

...

}

Here's the markup:

<uc1:MyUserControl ID="MyUserControl1" runat="server"
          TargetControlID="OkButton" />

I'm guessing the ID is out of scope and probably needs to be mangled to refer to the containment hierachy.  Any thoughts? Thanks in advance.

Set the id of the control with TargetControlId value in the page_Load of user control.

if am wrong Please explain the error scenarion .

Thanks a bunch.  Duh.  I forgot that the parent controls aren't instantiated yet when the accessor is called.  That's why I was getting a null reference exception.  For the benefit of all here's what to do:

 public partial class MyUserControl : System.Web.UI.UserControl
{

    private string _targetControlID;
    public string TargetControlID
    {
        get { return _targetControlID; }
        set { _targetControlID = value; }
    }


    protected void Page_Load(object sender, EventArgs e)
    {

        ModalPopupExtender1.TargetControlID = TargetControlID;
        ConfirmButtonExtender1.TargetControlID = TargetControlID;
    }
}