Can someone Explain Mutex and how it is used?

Question

I read a few documents about Mutex and still the only Idea I have got is that it helps preventing threads from accessing a resource that is already being used by another res

Answer 1

A mutex provides mutually exclusive access to a resource; in your case, a database. There aren't multiple threads in your program, but you can have multiple instances of your program running, which is what your mutex is protecting against. Effectively, it is still protecting against access from more than one thread, it's just that those threads can be in separate processes.

Your code is creating a named mutex that can be shared across multiple instances of your application. This is a form of interprocess communication. MSDN documentation on CreateMutex has additional helpful information about named mutexes:

Two or more processes can call CreateMutex to create the same named mutex. The first process actually creates the mutex, and subsequent processes with sufficient access rights simply open a handle to the existing mutex...

Multiple processes can have handles of the same mutex object, enabling use of the object for interprocess synchronization.

A mutex is only necessary here if the database you're working against doesn't inherently support multithreaded access.