C#只允许启动一个WinFrom进程

[STAThread]
public static void Main()
{
//Get the running instance.
Process instance = RunningInstance();
if (instance == null)
{
System.Windows.Forms.Application.EnableVisualStyles(); //这两行实现 XP 可视风格
System.Windows.Forms.Application.DoEvents();
//There isn't another instance, show our form.
Application.Run(new Main());
}
else
{
//There is another instance of this process.
HandleRunningInstance(instance);
}
}
public static Process RunningInstance()
{
Process current = Process.GetCurrentProcess();
Process[] processes = Process.GetProcessesByName(current.ProcessName);
//Loop through the running processes in with the same name
foreach (Process process in processes)
{
//Ignore the current process
if (process.Id != current.Id)
{
//Make sure that the process is running from the exe file.
if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == current.MainModule.FileName)
{
//Return the other process instance.
return process;
}
}
}
//No other instance was found, return null.
return null;
}
public static void HandleRunningInstance(Process instance)
{
//Make sure the window is not minimized or maximized
ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL);
//Set the real intance to foreground window
SetForegroundWindow(instance.MainWindowHandle);
}
[DllImport("User32.dll")]
private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
[DllImport("User32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);
private const int WS_SHOWNORMAL = 1;

[STAThread]
public static void Main()
{
bool ret;
System.Threading.Mutex mutex = new System.Threading.Mutex(true, Application.ProductName, out ret);
if (ret)
{
System.Windows.Forms.Application.EnableVisualStyles(); //这两行实现 XP 可视风格
System.Windows.Forms.Application.DoEvents();
System.Windows.Forms.Application.Run(new Main());
// Main 为你程序的主窗体，如果是控制台程序不用这句
mutex.ReleaseMutex();
}
else
{
MessageBox.Show(null, "有一个和本程序相同的应用程序已经在运行，请不要同时运行多个本程序。\n\n这个程序即将退出。", Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Warning);
// 提示信息，可以删除。
Application.Exit();//退出程序
}
}