public static class Cmd
{
    public static int Execute(string filename, string arguments)
    {
        var startInfo = new ProcessStartInfo
        {
            CreateNoWindow = true,
            FileName = filename,
            Arguments = arguments,
        };
        using (var process = new Process { StartInfo = startInfo })
        {
            try
            {
                process.Start();
                process.WaitForExit(30000);
                return process.ExitCode;
            }
            catch (Exception exception)
            {
                if (!process.HasExited)
                {
                    process.Kill();
                }
                return (int)ExitCode.Exception;
            }
        }
    }
}

gs -dNOPAUSE -q -sDEVICE=pnggray -r500 -dBATCH -dFirstPage=2 -dLastPage=2 -sOutputFile=test.png test.pdf