private static string CmdName = "cmd";
 /// <summary>
 /// 关闭进程
 /// </summary>
 /// <param name="processName">进程名</param>
 private void KillProcess(string processName)
 {
     Process[] myproc = Process.GetProcesses();
     foreach (Process item in myproc)
     {
         if (item.ProcessName == processName)
         {
             item.Kill();
         }
     }
 }

KillProcess(CmdName);