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copied!<p>Since it works correctly when the parent process is a console application, why not just temporarily turn it into one?</p> <pre><code>[DllImport("kernel32.dll")] [return: MarshalAs(UnmanagedType.Bool)] static extern bool AllocConsole(); [DllImport("kernel32.dll")] [return: MarshalAs(UnmanagedType.Bool)] static extern bool FreeConsole(); private static void Main(string[] args) { Process p = new Process(); p.StartInfo.UseShellExecute = false; p.StartInfo.CreateNoWindow = false; p.StartInfo.RedirectStandardOutput = true; p.StartInfo.RedirectStandardError = false; p.StartInfo.FileName = "Child.exe"; p.StartInfo.Arguments = "i"; AllocConsole(); p.Start(); FreeConsole(); string processOutput = p.StandardOutput.ReadToEnd(); p.WaitForExit(); Debug.WriteLine("The child process output is:" + processOutput); } </code></pre> <p>If you use a <code>lock</code> around <code>AllocConsole</code>/<code>Start</code>/<code>FreeConsole</code>, you can even start up multiple child processes, each with its own console window.</p> <hr> <p>This is an older 'solution' that did not work properly.</p> <p>Take a look at the <a href="http://msdn.microsoft.com/en-us/library/windows/desktop/ms684863.aspx" rel="nofollow">CreateProcess flags</a>. Not setting CREATE_NO_WINDOW doesn't give you a new console object; you need CREATE_NEW_CONSOLE. [nope, this was wrong; see below]</p> <p>Unfortunately, that isn't exposed in the .NET API. <code>Process.Start</code> does the right thing if you let it use <code>ShellExecute</code>, but then you can't redirect stdout. I think what you are trying to do is impossible with <code>System.Diagnostics.Process</code>, you will have to P/Invoke <code>CreateProcess</code>.</p> <p>Just yesterday I wrote my own <code>System.Diagnostics.Process</code> alternative because I needed another feature not provided by the MS implementation - redirect both stdout and stderr to the same stream. Feel free to reuse <a href="https://gist.github.com/dgrunwald/5331022" rel="nofollow">my code</a>, but keep in mind it didn't get much testing yet.</p> <p>I've tested your example with my <code>ProcessRunner</code>, and it works as expected if the parent process is a console application - the child gets its own new console window (not reusing the one from the parent as <code>System.Diagnostics.Process</code> does), it can <code>ReadKey()</code> from it, and stdout is redirected to the parent.</p> <p>But if the parent process is a windows application, this breaks down -- <code>ReadKey()</code> fails; and <code>stderr</code> output also isn't visible. (this is exactly the same behavior as <code>System.Diagnostics.Process</code>, I just didn't realize that <code>stderr</code> also wasn't working. The reason for this is that you can't just redirect one of the streams - as soon as <code>STARTF_USESTDHANDLES</code> is set, all the streams are redirected.</p> <p>Now I'm not sure why it works if the parent application is a console. Maybe the redirected stdin/stderr handles refer to the current console, not the console that was current when <code>GetStdHandle</code> was called.</p> <p>But if <code>GetStdHandle</code> is called within a Windows application, it returns INVALID_HANDLE. I'm not sure if there's a way to get a handle that will be valid once a console is created. Answer: do don't that, just create the console earlier (see new solution at beginning).</p>

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