Using the Windows API

In this post, we will look at how to use the Windows API to get and set windows in the Windows operating system.

First, create a new console app:

We will firstly add the Interop Services, which allows us to enable interop with DLLs:

using System.Runtime.InteropServices;

In our case, we will be using the user32.dll.

Next, we will use DllImport, which is part of the namespace we added, to reference the dll:

[DllImport("user32.dll")]

Finally, we can call a window function. In our case, we will call GetForegroundWindow. and print it to the console app:

[sourcecode language=”csharp”] using System;
using System.Text;
using System.Runtime.InteropServices;

namespace Carl.WindowsAPITest
{
class Program
{
[DllImport("user32.dll")] private static extern IntPtr GetForegroundWindow();

static void Main(string[] args)
{
IntPtr handle = GetForegroundWindow();
Console.ReadLine();
}
}
}
[/sourcecode]

Running this, we can see the what the handle returns:

We can also open Spy++ to see the handle value. To do this, in Visual Studio select Spy++:

This will open:

Select the Window Finder and drag the icon into the console app to see the same window handle: