System.Diagnostics.Process process = new System.Diagnostics.Process();
System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();

startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
startInfo.FileName = "cmd.exe";
startInfo.Arguments = "/C SomeEXE inputfile.txt";
startInfo.UseShellExecute = false;
startInfo.RedirectStandardOutput = true;

process.StartInfo = startInfo;
process.Start();

// Now use streams to capture the output
StreamReader outputReader = process.StandardOutput;

process.WaitForExit();

String line = outputReader.ReadToEnd();

startInfo.FileName = "SomeEXE";
startInfo.Arguments = "inputfile.txt";

myProcess.StartInfo.RedirectStandardInput = true;
StreamWriter myStreamWriter = myProcess.StandardInput;