This is what I use in my application:
static void Main()
{
bool mutexCreated = false;
System.Threading.Mutex mutex = new System.Threading.Mutex( true, @"Local\slimCODE.slimKEYS.exe", out mutexCreated );
if( !mutexCreated )
{
if( MessageBox.Show(
"slimKEYS is already running. Hotkeys cannot be shared between different instances. Are you sure you wish to run this second instance?",
"slimKEYS already running",
MessageBoxButtons.YesNo,
MessageBoxIcon.Question ) != DialogResult.Yes )
{
mutex.Close();
return;
}
}
// The usual stuff with Application.Run()
mutex.Close();
}