Why the lock in this code is not working ?

Question

I wrote simple code ( attached ) and i don't understand why the lock on some block is not locking the scope.

The code :

    object locker = new object();
    private void foo(int i)
    {
        Console.WriteLine( string.Format( "i is {0}", i ) );
        lock( locker )
        {
            while( true )
            {
                Console.WriteLine( string.Format( "i in while loop is {0}", i ) ) ;
                foo( ++i );
            }
        }
    }

I expect that the calling for the foo method in the while loop will be waiting until the locker will be release ( locker scope ) - but all the calls of the foo with arg of ++i can enter to the locker block.

Answer 1

The lock used here is reentrant. It will prevent another thread from entering the monitor, but the thread holding the lock will not be blocked.

Answer 2

Lock doesn't apply if you are on the same thread. See http://msdn.microsoft.com/en-us/library/c5kehkcz.aspx

Answer 3

The lock keyword is just syntactic sugar around the Monitor.Enter and Monitor.Exit methods. As seen in the documentation for Monitor:

It is legal for the same thread to invoke Enter more than once without it blocking;

Calling lock(object) from the same thread more than once has no effect other than to increase the lock count.