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.

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));
}

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