Conditions when finally does not execute in a .net try..finally block

47

Two possibilities:

• StackOverflowException
• ExecutionEngineException

The finally block will not be executed when there's a StackOverflowException since there's no room on the stack to even execute any more code. It will also not be called when there's an ExecutionEngineException, which may arise from a call to Environment.FailFast().

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• Perhaps worth noting that ExecutingEngineException may arise from a call to Environment.FailFast() - Daniel Fortunov
• What about OutOfMemoryException and ThreadAbortException? - Wiebe Tijsma
• B.T.W. I think it should be ExecutionEngineException instead of ExecutingEngineException? - Wiebe Tijsma
• I am getting a COM Context for this RuntimeCallableWraper failed error similar as described in stackoverflow.com/questions/36768352/… only I am using LINQ to SQL<br> This doesn't seems to be an exception in the usual manner and doesn't execute the finally block we have in place.<br> Has anyone seen this error before and can confirm if it does not execute the finally block? - Luke T O'Brien

14

Unless the CLR blows up and goes down with an ExecutingEngineException (I've seen a few in the .net 1.1 days with just the right amount of COM Interop :) .. I think finally should always execute.

5

You can get a situation where the code in the try block causes a SecurityException to be thrown before the try block entered (instead the exception is thrown when the containing method is called (see http://msdn.microsoft.com/en-us/library/fk6t46tz(VS.71).aspx)), in this situation you never even enter the try block so the code in the finally block is never called.

Other possibilities include StackOverflowException, and ExecutingEngineException.

3

Finally block on background thread may not execute. However, It depends upon the completed execution of main foreground thread which terminates background thread operation even before the complete execution of background thread.

class Program
{

    static void Main(string[] args)
    {
        Program prgm = new Program();
        Thread backgroundThread = new Thread(prgm.CheckBgThread);
        backgroundThread.IsBackground = true;
        backgroundThread.Start();
        Console.WriteLine("Closing the program....");
    }

    void CheckBgThread()
    {
        try
        {
            Console.WriteLine("Doing some work...");
            Thread.Sleep(500);
        }
        finally
        {
            Console.WriteLine("This should be always executed");
        }
    }
}

1

There is also Application.Exit method.

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• You mean Environment.Exit. Application.Exit allows the main routine to continue, so I'm sure Finally blocks are executed. - Mark Hurd

0

Neither code which follows a finally block, nor code in outer scopes, will execute without the finally block having been started first (an exception within the finally block may cause it to exit prematurely, in which case execution will jump out from the finalizer to an outer scope). If code prior to the finally block gets stuck in an endless loop or a method that never exits, or if the execution context is destroyed altogether, the finally block will not execute.

Note that it is proper to rely upon finally blocks, unlike "Finalize" methods (or C# "destructors") which should not properly be relied upon.