Listen to clipboard changes in a WPF application

To improve the UX, it can be useful to listen to clipboard changes. For instance, you can fill a 2FA code in a text box when the user copies it to the clipboard.

This can be done using the AddClipboardFormatListener function. Here is a simple example of how to listen to clipboard changes in a WPF application:

First, you need to add the Microsoft.Windows.CsWin32 package to your project. This package generate P/Invoke signatures for Windows APIs.

dotnet add package Microsoft.Windows.CsWin32

Then, you can add a file named NativeMethods.txt with the following content:

AddClipboardFormatListener
WM_CLIPBOARDUPDATE

Finally, you need to call the AddClipboardFormatListener function and listen to the WM_CLIPBOARDUPDATE message:

using System.Windows;
using System.Windows.Interop;
using Windows.Win32;
using Windows.Win32.Foundation;

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        Loaded += Window_Loaded;
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        if (PInvoke.AddClipboardFormatListener(new HWND(new WindowInteropHelper(this).Handle)))
        {
            ComponentDispatcher.ThreadFilterMessage += ComponentDispatcher_ThreadFilterMessage;
        }
    }

    private void ComponentDispatcher_ThreadFilterMessage(ref MSG msg, ref bool handled)
    {
        if (msg.message == PInvoke.WM_CLIPBOARDUPDATE)
        {
            // Clipboard content has changed
            Console.WriteLine(Clipboard.GetText());
        }
    }
}

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