Solution 1:

Use RedirectStandardOutput.

Sample from MSDN:

// Start the child process.
Process p = new Process();
// Redirect the output stream of the child process.
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.FileName = "Write500Lines.exe";
p.Start();
// Do not wait for the child process to exit before
// reading to the end of its redirected stream.
// p.WaitForExit();
// Read the output stream first and then wait.
string output = p.StandardOutput.ReadToEnd();
p.WaitForExit();

Also see OutputDataReceived and BeginOutputReadLine() for an alternative to ReadToEnd(), that will better fulfill your "see output while the process is running" requirement.

Solution 2:

If you want to execute an exe from your c# application and get the output from it then you can use the below code

System.Diagnostics.Process p = new System.Diagnostics.Process();            

p.StartInfo.FileName = "PATH TO YOUR FILE";
p.StartInfo.UseShellExecute = false;
p.StartInfo.Arguments = metalType + " " + graphHeight + " " + graphWidth;
p.StartInfo.CreateNoWindow = true;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.RedirectStandardError = true;              

p.EnableRaisingEvents = true;
p.Start();            
svgText = p.StandardOutput.ReadToEnd();

using(StreamReader s = p.StandardError)
{
    string error = s.ReadToEnd();
    p.WaitForExit(20000);
}

Don't forgete to write p.EnableRaisingEvents = true;