用C#让应用程序只有一个实例在运行

//原代码很乱，整理了一下

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

public class OneInstnace
{

//Api声明，并声明一

 [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()
 {   
  //得到正在运行的例程   
  Process instance = RunningInstance();   
  if (instance == null)
  {
   //如果没有其它例程，就新建一个窗体     
   Application.Run (new Form());   
  }   
  else   
  {
   //处理发现的例程
   HandleRunningInstance(instance);
  }
 }
 public static Process RunningInstance() 
 {
  Process current = Process.GetCurrentProcess();
  Process[] processes = Process.GetProcessesByName (current.ProcessName);
  //遍历正在有相同名字运行的例程   
  foreach (Process process in processes)   
  {
   //忽略现有的例程     
   if (process.Id != current.Id)
   {
    //确保例程从EXE文件运行       
    if (Assembly.GetExecutingAssembly().Location.Replace("/", "//") ==current.MainModule.FileName)
    {
     //返回另一个例程实例         
     return process;
    }
   }
  }
  //没有其它的例程，返回Null   
  return null; 
 }
 public static void HandleRunningInstance(Process instance)
 {
  //确保窗口没有被最小化或最大化   
  ShowWindowAsync (instance.MainWindowHandle , WS_SHOWNORMAL);  
  //设置真实例程为foreground window   
  SetForegroundWindow (instance.MainWindowHandle);
 }

}