How to implement single instance per machine application?

Question

I have to restrict my .net 4 WPF application so that it can be run only once per machine. Note that I said per machine, not per session.
I implemented single instance applications using a simple mutex until now, but unfortunately such a mutex is per session.

Is there a way to create a machine wide mutex or is there any other solution to implement a single instance per machine application?

Answer 1

I would do this with a global Mutex object that must be kept for the life of your application.

MutexSecurity oMutexSecurity;

//Set the security object
oMutexSecurity = new MutexSecurity();
oMutexSecurity.AddAccessRule(new MutexAccessRule(new SecurityIdentifier(WellKnownSidType.BuiltinUsersSid, null), MutexRights.FullControl, AccessControlType.Allow));

//Create the global mutex and set its security
moGlobalMutex = new Mutex(True, "Global\\{5076d41c-a40a-4f4d-9eed-bf274a5bedcb}", bFirstInstance);
moGlobalMutex.SetAccessControl(oMutexSecurity);

Where bFirstInstance returns if this is the first instance of your application running globally. If you omited the Global part of the mutex or replaced it with Local then the mutex would only be per session (this is proberbly how your current code is working).

I believe that I got this technique first from Jon Skeet.

The MSDN topic on the Mutex object explains about the two scopes for a Mutex object and highlights why this is important when using terminal services (see second to last note).