How do I add an ASP.NET control inside an ASCX to an external RequiredFieldValidator programmatically?

Question

I have a drop-down list inside a user control (ASCX) that I want to validate from the page on which I've placed the ASCX, but when I set the ControlToValidate to the drop-down list the page complains that it can't be found. Thanks for any help/suggestions.

Answer 1

Expose the dropdown list with a public property in your user control:

public DropDownList DropDownToValidate
    {
        get
        {
            return ddlTest;
        }
    }

Then use the UniqueID of the exposed Dropdown to set the control to validate in the page load of the page on which you dropped the user control:

protected void Page_Load(object sender, EventArgs e)
{

    RequiredFieldValidator1.ControlToValidate = WebUserControl1.DropDownToValidate.UniqueID;
}