It’s always the Invoke

If you are working on the .NET Compact Framework 1.0 and you get an ArgumentException trying to manipulate your UI (such as adding a Control to a form), you are likely doing this operation from a thread other than you UI thread and should be using Invoke. Thanks to jonfroelich‘s post “Controls.Add ArgumentException” for putting me on the right path. With all my frustrating debugging and unexplained freezes, i’d completely forgot that the particular code branch I was looking at was initiated by a callback from a WorkerThread.

Of course the Invoke facilities of .NETCF 1.0 are pitiful, lacking the things that make this whole single-threaded UI business bearable in regular Windows.Forms. There is not InvokeRequired for one thing, nor is there BeginInvoke. And even Invoke just provides the Invoke(Delegate) signature, not the much more useful Invoke(Delegate, Object[]).

Add to that that the only valid Delegate is an EventHandler, which takes two arguments, the exclusion of Invoke(Delegate, Object[]) really is painful.