Visual Studio: ContextSwitchDeadlock

Question

The ContextSwitchDeadlock doesn't necessarily mean your code has an issue, just that there is a potential. If you go to Debug > Exceptions in the menu and expand the Managed Debugging Assistants, you will find ContextSwitchDeadlock is enabled.

If you disable this, VS will no longer warn you when items are taking a long time to process. In some cases you may validly have a long-running operation. It's also helpful if you are debugging and have stopped on a line while this is processing - you don't want it to complain before you've had a chance to dig into an issue.

In Visual Studio 2017, unchecked the ContextSwitchDeadlock option by:

Debug > Windows > Exception Settings

In Exception Setting Windows: Uncheck the ContextSwitchDeadlock option

As Pedro said, you have an issue with the debugger preventing the message pump if you are stepping through code.

But if you are performing a long running operation on the UI thread, then call Application.DoEvents() which explicitly pumps the message queue and then returns control to your current method.

However if you are doing this I would recommend at looking at your design so that you can perform processing off the UI thread so that your UI remains nice and snappy.

It sounds like you are doing this on the main UI thread in the app. The UI thread is responsible for pumping windows messages as the arrive, and yet because yours is blocked in database calls it is unable to do so. This can cause problems with system wide messages.

You should look at spawning a background thread for the long running operation and putting up some kind of "I'm busy" dialog for the user while it happens.

If you don't want to disable this exception, all you need to do is to let your application pump some messages at least once every 60 seconds. It will prevent this exception to happen. Try calling System.Threading.Thread.CurrentThread.Join(10) once in a while. There are other calls you can do that let the messages pump.

The above solution is good in some scenarios but there is another scenario where this happens when you are unit testing and you try to "Debug Selected Tests" from the Test Explorer when you solution is not set to Debug.

In this case you need to change your solution from Release or whatever it is set to to Debug in this case. If this is the problem then changing "ContextSwitchDeadlock" won't really help you.

I missed this myself because the error message was so nasty I didn't check the obvious thing which was the Debug setting!

In Visual Studio 2017 Spanish version.

"Depurar" -> "Ventanas" -> "Configuración de Excepciones"

and search "ContextSwitchDeadlock". Then, uncheck it. Or shortcut

Ctrl+D,E

Best.