C#让程序只运行一次实例

添加引用

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

调用DLL文件

[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 ;

添加如下两个函数

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);
}

在MAIN中添加如下代码

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