Programın arka planda çalışması nasıl engellenir?

[DllImport("user32.dll")]
private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
[DllImport("user32.dll")]
private static extern void SwitchToThisWindow(IntPtr hWnd, bool fAltTab);
[DllImport("user32.dll", SetLastError = true)]
private static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
private const int SW_RESTORE = 9;
[STAThread]
private static void Main()
{
    System.Threading.Thread.Sleep(999);
    foreach (var process in Process.GetProcesses())
    {
        try
        {
            if (process.ProcessName.Contains("Form1"))
            {
                IntPtr mainWindowHandle = process.MainWindowHandle;
                if (mainWindowHandle != IntPtr.Zero || FindWindow(null, "Form1") != IntPtr.Zero)
                {
                    SwitchToThisWindow(mainWindowHandle, true);
                    ShowWindow(mainWindowHandle, SW_RESTORE);
                    Application.Exit();
                    return;
                }
            }
        }
        catch { }
    }
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);
    Application.Run(new Form1());
}