The other answers are correct. Here is some code you could use:
ProcessStartInfo startInfo = new ProcessStartInfo(cmd, args);
startInfo.UseShellExecute = false;
startInfo.RedirectStandardError = true;
Process someProcess = Process.Start(startInfo);
string errors = someProcess.StandardError.ReadToEnd();
Note that if the file is not found you won't get an error on standard error. You will get an exception instead.
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