Video tip C#: Ensure only one instance is running

[STAThread]
static void Main()
{
    bool singLeInstance = true;
    Mutex mutex = new Mutex(true, "UniqueApplicationName", out onlyInstance);
    if (!singleInstance) {
    return;
}
else
{
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);
    Application.Run(new Form1());
}