学习打卡 WPF应用创建单实例窗口

不懂，不会，看不明白，做个记录，以后用得到

····public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            Mutex mutex = new Mutex(true, "单实例程序", out bool isNewInstance);
            if (isNewInstance!= true) {
                //MessageBox.Show("程序已启动");
                IntPtr intPtr = FindWindowW(null, "单实例窗口");
                if (intPtr != IntPtr.Zero) {
                    SetForegroundWindow(intPtr);
                }
                Shutdown();
            }
        }
        [DllImport("User32", CharSet = CharSet.Unicode)]
        static extern IntPtr FindWindowW(String lpClassName, String lpWindowName);

        [DllImport("User32", CharSet = CharSet.Unicode)]
        static extern Boolean SetForegroundWindow(IntPtr hWnd);
    }