Question

I have a WPF application with a form that, when started, invokes a custom method in a new thread.

Private Sub TestStep1_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
    Dim oThread As New Thread(AddressOf DisplayNextPicture)
    oThread.Start()
End Sub

Private Sub DisplayNextPicture()
    '' do stuff
End Sub

This works fine on my machine, but on a client’s machine the launching of the new thread results in a MissingMethodException. I’m not sure why this would happen (and unfortunately the client is in a remote location so I’m having to debug this by slipping in trace statements and trial and error). It is definitely the DisplayNextPicture() method that is not being found, as I’ve been able to determine via tracing.

The only thing I can think of is that this has to do with security at the framework level. Are there restrictions on launching new threads from a WPF application?

I’m unable to catch this exception via Application.DispatcherUnhandledException so I cannot get any exception details or stack trace. The client gets a .NET runtime exception dialog with the following info and this is the only way I know the exception type:

EventType : clr20r3 P1 : testapp.exe P2 : 1.0.0.0 P3 : 49fa2234
P4 : mscorlib P5 : 2.0.0.0 P6 : 471ebc5b P7 : 1295 P8 : 14
P9 : system.missingmethodexception

Please help 🙂

Answer 1

Just encountered this issue when attempting to run a Windows Service (which I had written). The service would run fine on my test environment but not on a different machine.

The problem turned out to be that the troublesome machine was running Framework version 3.5 while my development machine was on 3.5 Service Pack 1. Upgrading the machine to SP1 fixed the issue.

Hope this eases someone’s pain a little.