Question

I’m doing this:

    Delegate Sub SetTextBoxText_Delegate(ByVal [Label] As TextBox, ByVal [text] As String)
' The delegates subroutine.  

Public Sub SetTextBoxText_ThreadSafe(ByVal [Label] As TextBox, ByVal [text] As String)
    ' InvokeRequired required compares the thread ID of the calling thread to the thread ID of the creating thread.  
    ' If these threads are different, it returns true.  
    If [Label].InvokeRequired Then
        MsgBox("invoke")
        Dim MyDelegate As New SetTextBoxText_Delegate(AddressOf SetTextBoxText_ThreadSafe)
        Me.Invoke(MyDelegate, New Object() {[Label], [text]})
    Else
        MsgBox("noinvoke")
        [Label].Text = [text]
    End If
End Sub

However it always uses noinvoke. If I try setting it normaly it gives me a thread-safe warning and doesn’t work. If I force invoke then it says the control isn’t created?

Could someone help?

Answer 1

It’s most likely because the control has not yet been created when you try to access it. Wait until the control has loaded, or check it using Label.Created. Like so:

Public Sub SetTextBoxText_ThreadSafe(ByVal Label As TextBox, ByVal text As String)
    If Label.Created Then
        If Label.InvokeRequired Then
            MsgBox("invoke")
            Dim MyDelegate As New SetTextBoxText_Delegate(AddressOf SetTextBoxText_ThreadSafe)
            Me.Invoke(MyDelegate, New Object() {Label, text})
        Else
            MsgBox("noinvoke")
            Label.Text = text
        End If
    End If
End Sub

P.S. You don’t need a custom delegate type, just use Action(Of TextBox, String). You also don’t need square brackets around Label or text.