Output To Console In Windows Forms Application

On September 1, 2009 · 13 Comments

This post shows you how to output data to a Console in a Windows Forms Application. I use this technique religiously when developing Windows Forms applications. Debugging is much simpler when you can see information on what your application is doing in a Console. Of course the onus is on you as developer to output data which will help you.

In this post I will use a simple Windows Forms application which adds two numbers.

Windows Forms

By default a Windows Forms application does not output to a Console even if you write a Console.Write() or Console.WriteLine(). This shortcoming can be addressed by using Win32 API. In your Windows Forms application you can declare a class which provides a wrapper around Win32 functions.

public class Win32
{
  /// <summary>
  /// Allocates a new console for current process.
  /// </summary>
  [DllImport("kernel32.dll")]
  public static extern Boolean AllocConsole();

  /// <summary>
  /// Frees the console.
  /// </summary>
  [DllImport("kernel32.dll")]
  public static extern Boolean FreeConsole();
}

A Console must be started to accept input and display our messages. This can be done by calling Win32.AllocConsole() function. For my example I will start the console in my form’s constructor.

public Form1()
{
  InitializeComponent();

  Win32.AllocConsole();
}

Now when I write to Console, I will see data appear in the console window which was started in my constructor.

private void Add(int num1, int num2)
{
  int result = num1 + num2;

  Console.WriteLine(
    string.Format("{0} + {1} = {2}", num1, num2, result));
}

Console

As a good practice you should also close the console window by calling Win32.FreeConsole() method before your application exits.

Tagged with: C# • Win32 • Windows Forms

13 Responses to Output To Console In Windows Forms Application

Kevin says:

September 3, 2009 at 10:56 pm

Thanks for the tip. Too bad Console.Clear does not work under Vista although works fine under XP.
Ed says:

September 14, 2009 at 5:48 am

Thanks, just what I needed
Deepak says:

September 14, 2009 at 9:12 am

Thanks Ed. I’m glad that you found this article helpful.
Chandra says:

September 17, 2009 at 11:33 am

It is great. Very helpful
Thank you.
Akshay says:

November 4, 2009 at 7:59 pm

It worked.
Thanks !
Bob says:

May 27, 2010 at 9:12 am

Thank you for publishing this solution. I have tried several different offered solution and yours is the only one the worked the very first time. Great job!
Deepak says:

May 27, 2010 at 9:53 am

Bob, Thanks for your motivating comment.
pgn674 says:

September 7, 2010 at 2:04 pm

This worked for me after I added
using System.Runtime.InteropServices;
Thanks for the how-to.
OMFG says:

July 6, 2011 at 11:40 pm

You, sir, deserve a medal.

I’ve been to 5 different sites where people invent the most cumbersome and enormous code to accomplish what you did in a simple and elegant manner.

Thank you.

Also thanks to pgn674 for the useful comment.
Deepak says:

July 7, 2011 at 9:18 am

OMFG, thanks and I gladly accept the medal :)
Sambo says:

August 20, 2011 at 1:21 pm

Thanks Deepak, good work
Pantelis says:

September 29, 2011 at 2:41 am

Guys can someone transfer this to c++ ?
John says:

December 16, 2011 at 12:00 am

When closing the allocated console it causes the termination of the main application.
Is there a way to prevent it?