ProcessStartInfo.UseShellExecute 属性需要设置为true

Process proc = new Process();
proc.StartInfo.UseShellExecute = true;
proc.StartInfo.CreateNoWindow = true;
proc.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
proc.StartInfo.FileName =  "cmd.exe";
proc.StartInfo.RedirectStandardError = false;
proc.StartInfo.RedirectStandardOutput = false;
proc.Start();
proc.WaitForExit();

[参考]
​​​ProcessStartInfo.UseShellExecute 属性​​​​从Process.Start C＃隐藏控制台窗口​​