Question

I developed a WPF Application where I have problems when closing the application.

Only on Windows 2003 PCs, the application throws the following exception on closing. But it does not seem to be thrown from my code, because I can’t get a callstack.

That’s why I can’t post any further details.

Do you have a clue where I can start digging into it?

System.InvalidOperationException was unhandled
  Message=Handle is not initialized.
  Source=mscorlib
  StackTrace:
       at System.WeakReference.set_Target(Object value)
       at System.Windows.Threading.Dispatcher.FromThread(Thread thread)
       at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
       at MS.Win32.UnsafeNativeMethods.IntDestroyWindow(HandleRef hWnd)
       at MS.Win32.HwndWrapper.DestroyWindow(Object args)
       at MS.Win32.HwndWrapper.Dispose(Boolean disposing, Boolean isHwndBeingDestroyed)
       at MS.Win32.HwndWrapper.Finalize()
  InnerException: 

Thanks for your ideas.

EDIT
I found out which lines of code produces the failure. But how can I fix it?

It’s the following line of code:

        try
        {
            return DesignerProperties.GetIsInDesignMode(new DependencyObject());
        }
        catch (Exception)
        {
            return true;
        }

I’m using this to check if the code runs in the designer. But on closing this code fails, although I catched the exception.

Any other ideas to check the designmode?
Thanks for your help.

Answer 1

To answer my own question …

I could solve the issue by implementing a backing field for the IsInDesignMode Property. The backing field is now going to bet set within the constructor of the ViewModel, instead of my prior solution which checked the DesignMode on every method call.

That means, that even within the Dispose Method it can be checked if the application is/was running in DesignMode.