Clipboard event C#

Question

Is there a clipboard changed or updated event that i can access through C#?

Answer 1

I had this challenge in WPF and ended up using the approach described below. For windows forms there are excellent examples elsewhere in this answer, such as the ClipboardHelper control.

For WPF we cannot override WndProc, so we have to hook it explicitly with an HwndSource AddHook call using the Source from a window. The clipboard listener still uses the AddClipboardFormatListener native interop call.

Native methods:

internal static class NativeMethods
{
    // See http://msdn.microsoft.com/en-us/library/ms649021%28v=vs.85%29.aspx
    public const int WM_CLIPBOARDUPDATE = 0x031D;
    public static IntPtr HWND_MESSAGE = new IntPtr(-3);

    // See http://msdn.microsoft.com/en-us/library/ms632599%28VS.85%29.aspx#message_only
    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool AddClipboardFormatListener(IntPtr hwnd);
}

Clipboard Manager class:

using System.Windows;
using System.Windows.Interop;

public class ClipboardManager
{
    public event EventHandler ClipboardChanged;

    public ClipboardManager(Window windowSource)
    {
        HwndSource source = PresentationSource.FromVisual(windowSource) as HwndSource;
        if(source == null)
        {
            throw new ArgumentException(
                "Window source MUST be initialized first, such as in the Window's OnSourceInitialized handler."
                , nameof(windowSource));
        }

        source.AddHook(WndProc);

        // get window handle for interop
        IntPtr windowHandle = new WindowInteropHelper(windowSource).Handle;

        // register for clipboard events
        NativeMethods.AddClipboardFormatListener(windowHandle);
    }

    private void OnClipboardChanged()
    {
        ClipboardChanged?.Invoke(this, EventArgs.Empty);
    }

    private static readonly IntPtr WndProcSuccess = IntPtr.Zero;

    private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        if (msg == NativeMethods.WM_CLIPBOARDUPDATE)
        {
            OnClipboardChanged();
            handled = true;
        }

        return WndProcSuccess;
    }
}

This gets used in a WPF window by adding the event in OnSourceInitialized or later such as the Window.Loaded event or during operation. (when we have enough information to use the native hooks):

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    protected override void OnSourceInitialized(EventArgs e)
    {
        base.OnSourceInitialized(e);

        // Initialize the clipboard now that we have a window soruce to use
        var windowClipboardManager = new ClipboardManager(this);
        windowClipboardManager.ClipboardChanged += ClipboardChanged;
    }

    private void ClipboardChanged(object sender, EventArgs e)
    {
        // Handle your clipboard update here, debug logging example:
        if (Clipboard.ContainsText())
        {
            Debug.WriteLine(Clipboard.GetText());
        }
    }
}

I'm using this approach in a Path of Exile item analyzer project, as the game exposes item information via the clipboard when you hit Ctrl-C.

https://github.com/ColinDabritz/PoeItemAnalyzer

I hope this helps someone with WPF clipboard change handling!