Question

I was wondering which of the following was the suggested pattern when using Mutex (or Semaphores or ReadWriteLockSlims etc.).

Should the initial lock happen inside or outside of the try statement? Is it unimportant?

_mutex.WaitOne()
try
{
 // critical code
}
finally
{
  _mutex.ReleaseMutex();
}

or

try
{
  _mutex.WaitOne()
 // critical code
}
finally
{
  _mutex.ReleaseMutex();
}

Answer 1

Maybe it is a different. Take a look into these posts from Eric:

• Subtleties of C# IL codegen
• Locks and exceptions do not mix

In short:
Just imagine there happens an exception between the mutex.WaitOne() and the try statement. You’ll leave this chunk of code without calling the _mutex.ReleaseMutex().

So take your second piece of code to be sure everything works as expected.