Hi

Many a time we do not want the user to create the second instance of the (Windows) Application on the same machine. For this we need to restrict the user from opening more than one instance of the application.

The notion of Global and mutex has been introduced by Microsoft to solve this problem. Things like Citrix might fail in condition were you have multi user session (terminal service)

We use the following code to restrict the use of two instance of an application.

  Mutex instanceLock = new Mutex(false, "Name of the Assembly");

            if (instanceLock.WaitOne(0, false))

            {

                try

                {

                    Application.EnableVisualStyles();

                    Application.SetCompatibleTextRenderingDefault(false);

                    Application.Run(new frmMain());

                }

                finally

                { instanceLock.ReleaseMutex(); }

            }

            else

            {

                MessageBox.Show("You cannot have two instance of this application running");

                Application.Exit();

            }

[Note: the mutex class is in System.Threading class]

Hope this helps
Thanks
Vikram