Sample console app that redirects stdout and stderr from another process to the current error and output streams

Program.cs

public class Program
{
	public static void Main(string[] args)
	{
		var processStartInfo = new ProcessStartInfo
		{
			FileName = "C:\\foo.exe",
			RedirectStandardOutput = true,
			RedirectStandardError = true,
			UseShellExecute = false,
		};

		using (var process = Process.Start(processStartInfo))
		{
			process.OutputDataReceived += (sender, output) =>
			{
				Console.WriteLine(output.Data);
			};
			process.ErrorDataReceived += (sender, output) =>
			{
				Console.Error.WriteLine(output.Data);
			};
			process.BeginOutputReadLine();
			process.WaitForExit();
		}
	}
}