Using Windows Notepad as an output console

Question

If there is a way to direct an ascii output to Windows notepad. Scenario: an application starts notepad instance of Windows Notepad or finds one. Than the application pushes some text messages to the notepad so that the message appends to the opened notepad text.

Answer 1

Raymond Chen has a blog and made a post describing something similar, maybe you can adapt it to what you want? Link

Edit: Relevant code from the blog

using System;
using System.Diagnostics;
using System.Windows.Automation;
using System.Runtime.InteropServices;

class Program
{
  static void Main(string[] args)
  {
    // Slurp stdin into a string.
    var everything = Console.In.ReadToEnd();

    // Fire up a brand new Notepad.
    var process = new Process();
    process.StartInfo.UseShellExecute = false;
    process.StartInfo.FileName = @"C:\Windows\System32\notepad.exe";
    process.Start();
    process.WaitForInputIdle();

    // Find the Notepad edit control.
    var edit = AutomationElement.FromHandle(process.MainWindowHandle)
        .FindFirst(TreeScope.Subtree,
                   new PropertyCondition(
                       AutomationElement.ControlTypeProperty,
                       ControlType.Document));

    // Shove the text into that window.
    var nativeHandle = new IntPtr((int)edit.GetCurrentPropertyValue(
                      AutomationElement.NativeWindowHandleProperty));
    SendMessage(nativeHandle, WM_SETTEXT, IntPtr.Zero, everything);
  }

  [DllImport("user32.dll", EntryPoint="SendMessage", CharSet=CharSet.Unicode)]
  static extern IntPtr SendMessage(
    IntPtr windowHandle, int message, IntPtr wParam, string text);
  const int WM_SETTEXT = 0x000C;
}

Answer 2

You can send the text to the Process with SendKeys.SendWait:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace SendKeysToProcess
{
    class Program
    {
        [DllImport("user32.dll")]
        static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

        static void Main(string[] args)
        {
            // Start Notepad process
            Process notepad = new Process();
            notepad.StartInfo.FileName = @"C:\Windows\Notepad.exe";
            notepad.Start();

            // Wait for notepad to start
            notepad.WaitForInputIdle();

            IntPtr p = notepad.MainWindowHandle;
            ShowWindow(p, 1);

            // Write some text to the Notepad window
            SendKeys.SendWait("Hello World!");
        }
    }
}