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)
;
    }
}

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