public static void KillProcess(string strProcessesByName)//關閉執行緒
        {
            foreach (Process p in Process.GetProcesses())//GetProcessesByName(strProcessesByName))
            {
                if (p.ProcessName.ToUpper().Contains("你要關閉的程序名字"))
                {
                    try
                    {
                        p.Kill();
                        p.WaitForExit(); 
 
// possibly with a timeout
                    }
                    catch (Win32Exception e)
                    {
                        MessageBox.Show(e.Message.ToString());   // process was terminating or can't be terminated - deal with it
                    }
                    catch (InvalidOperationException e)
                    {
                        MessageBox.Show(e.Message.ToString()); 
 
// process has already exited - might be able to let this one go
                    }
                }
            }
        }

或者這樣關閉自己

 Environment.Exit(0);