I'm reviewing some code for a friend and say that he was using a return statement inside of a try-finally block. Does the code in the Finally section still fire even though the rest of the try block doesn't?
Example:
public bool someMethod()
{
try
{
return true;
throw new Exception("test"); // doesn't seem to get executed
}
finally
{
//code in question
}
}
Normally, yes. The finally section is guaranteed to execute whatever happens including exceptions or return statement. An exception to this rule is an asynchronous exception happening on the thread (ThreadAbortException, OutOfMemoryException, StackOverflowException).
To learn more about async exceptions and reliable code in that situations, read about constrained execution regions.
Yes. That is in fact that main point of a finally statement. Unless something catestrophic occurs (out of memory, computer unplugged, etc.) the finally statement should always be executed.
Not to be rude, but whenever I have something like, "how does the framework handle X?", I just make a little sample console app and try it out. Especially when it's something simple like this. You could basically paste your code above into a .cs file, compile it in the VS command line, and have your answer in a matter of seconds.
Quoting from MSDN
finally is used to guarantee a statement block of code executes regardless of how the preceding try block is exited.
In response to Perpetualcoder - normally the finally is guaranteed to fire, but as has been noted above, there are certain cases where this won't apply. For instance, if you have a StackOverflowException, the application comes to a sudden halt - so the finally block never gets called.
Bottom line - MSDN does not always equal truth.
Here's a little test:
class Class1
{
[STAThread]
static void Main(string[] args)
{
Console.WriteLine("before");
Console.WriteLine(test());
Console.WriteLine("after");
}
static string test()
{
try
{
return "return";
}
finally
{
Console.WriteLine("finally");
}
}
}
The result is:
before
finally
return
after