只运行程序1个实例

private   bool   PrevInstance()  
{
string   procName   =   System.Diagnostics.Process.GetCurrentProcess().ProcessName;  
if((System.Diagnostics.Process.GetProcessesByName(procName)).GetUpperBound(0)   > 0)  
{  
return   true;  
}  
else  
{  
return   false;  
}  
}