C# 调用CMD，执行DOS命令

Process p = new Process();
   p.StartInfo.FileName = "cmd.exe";
   p.StartInfo.UseShellExecute = false;
   p.StartInfo.RedirectStandardInput = true;
   p.StartInfo.RedirectStandardOutput = true;
   p.StartInfo.RedirectStandardError = true;
   p.StartInfo.CreateNoWindow = true;
   p.Start();
   string strOutput=null;
//   p.StandardInput.WriteLine("cd D:\\flv\\mplayer");
//   p.StandardInput.WriteLine("cd d:");
   p.StandardInput.WriteLine(string.Format("D:\\flv\\mplayer\\mencoder \"c:\\vs.wmv\" -o \"c:\\output.flv\" -of lavf  -lavfopts i_certify_that_my_video_stream_does_not_use_b_frames -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate={0}:mbd=2:mv0:trell:v4mv:cbp:last_pred=3:dia=4:cmp=6:vb_strategy=1 -vf scale=512:-3 -ofps 12 -srate 22050",200));
  
   p.StandardInput.WriteLine("exit");
   strOutput = p.StandardOutput.ReadToEnd();
   Console.WriteLine(strOutput);
   p.WaitForExit();
   p.Close();