软件进程只能存在一个

判断系统是否已经在运行了:      using System.Threading;

bool bOnlyOneInstance = false;            

Mutex mutex = new Mutex(true, Application.UserAppDataPath.Replace(@"\", "_"), out   bOnlyOneInstance);            

if (!bOnlyOneInstance)            

 {                

MessageBox.Show("系统已经运行!", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);                 return;            

 }            

else            

 {                

Application.EnableVisualStyles();                

Application.SetCompatibleTextRenderingDefault(false);                

 Application.Run(new GBIM_Login());            

}