C#让程序只运行一次实例

using System.Reflection;
using System.Runtime.InteropServices;
using System.Diagnostics;

[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;

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);
}

public static void Main()
{
Process instance = RunningInstance();
if (instance == null)
{
Application.Run(new Form1());
}
else
{
HandleRunningInstance(instance);
}
}