Question

This may sounds stupid, but I can’t access a progressbar in another thread. Yes, I’ve invoked it. Check it out:

Delegate Sub ProgressBarCallback(ByVal value As Integer, ByVal max As Integer)


Sub updateProgressBarCurrent(ByVal value As Integer, ByVal max As Integer)

    If Me.progressBar_currentState.InvokeRequired = True Then
        Dim d As New ProgressBarCallback(AddressOf updateProgressBarCurrent)
        Me.progressBar_currentState.Invoke(d, New Object() {value, max})
    Else
        progressBar_currentState.Maximum = max
        If value < max Then
            progressBar_currentState.Value = value
            progressBar_currentState.Refresh()
        End If
    End If

End Sub

I’m calling updateProgressBarCurrent() from a method inside a class. Have a look at the debugger:

The ProgressBar just doesn’t do anything. Is this because I’m calling the sub updateProgressBarCurrent from a method in my databaseHandler class? How can I fix this?
Thanks in advance.

Answer 1

Are you using the “default instance” feature for Forms? Kind of No-Go in multithreaded apps!
There is ONE default instance for EACH thread. So if you call Form1.DoSomething from another thread, you are not calling “your” Form1 but instead a new (invisible, not shown) instance of your Form1.