Question

I am working with a page and I am getting an Page.IsValid = false and I am trying to determine which control is causing the validation problem.

Answer 1

In code (page_load), you can do this:
(per MSDN: http://msdn.microsoft.com/en-US/library/dh9ad08f%28v=VS.80%29.aspx)

If (Me.IsPostBack) Then
    Me.Validate()
    If (Not Me.IsValid) Then
        Dim msg As String
        ' Loop through all validation controls to see which 
        ' generated the error(s).
        Dim oValidator As IValidator
        For Each oValidator In Validators
            If oValidator.IsValid = False Then
                msg = msg & "<br />" & oValidator.ErrorMessage
            End If
        Next
        Label1.Text = msg
    End If
End If

In the markup, you can…

• You can put “text” on your validator (like an
  asterisk…)
• Or use a validation_summary control (which requires an error message on your validator)…