Mutex

http://www.albahari.com/threading/part2.aspx#_Mutex

A Mutex is like a C# lock, but it can work across multiple processes.

In other words, Mutex can be computer-wideas well as application-wide.

Note:

Acquiring and releasing an uncontended Mutex takes a few microseconds — about 50 times slower than a lock.

With a Mutex class, you call the WaitOne method to lock and ReleaseMutex to unlock.

Closing or disposing a Mutex automatically releases it.

Just as with the lock statement, a Mutex can be released only from the same thread that obtained it.

A common use for a cross-process Mutex is to ensure that only one instance of a program can run at a time.

Here’s how it’s done:

class OneAtATimePlease
    {
        static void Method()
        {
            //Naming a Mutex makes it available computer-wide. 
            //Use a name that's unique to your company and application (e.g., include your URL).
            using (var mutex = new Mutex(false, "oreilly.com OneAtATimeDemo"))
            {
                //Wait a few seconds if contended, in case another instance of the program is still in the process of shutting down.
                if (mutex.WaitOne(TimeSpan.FromSeconds(3), false) == false)
                {
                    Console.WriteLine("Another app instance is running. Bye!");
                    return;
                }
                RunProgram();
            }
        }

        static void RunProgram()
        {
            Console.WriteLine("Running. Press Enter to exit");
            Console.ReadLine();
        }
    }

Note:

If running under Terminal Services, a computer-wide Mutex is ordinarily visible only to applications in the same terminal server session.

To make it visible to all terminal server sessions, prefix its name with Global.

Mutex Class

A synchronization primitive that can also be used for interprocess synchronization.

Mutex(Boolean, String, Boolean)

Initializes a new instance of the Mutex class with a Boolean value that indicates whether the calling thread should have initial ownership of the mutex, a string that is the name of the mutex, and a Boolean value that, when the method returns, indicates whether the calling thread was granted initial ownership of the mutex.

[System.Security.SecurityCritical]
public Mutex (bool initiallyOwned, string name, out bool createdNew);