source: 2015/koodauskerho/otjojunt/WpfHarjoitus1/WpfHarjoitus1/ClipboardListener.cs @ 7058

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

public sealed class ClipboardListener
{
    private static ClipboardListener instance = new ClipboardListener();

    public delegate void ClipboardUpdateHandler(string contents);

    /// <summary>
    /// Tapahtuu kun leikepöydän sisältö muuttuu
    /// </summary>
    public static event ClipboardUpdateHandler ClipboardUpdate;

    private static NotificationForm _form = new NotificationForm();

    private class NotificationForm : Form
    {
        public NotificationForm()
        {
            NativeMethods.SetParent(Handle, NativeMethods.HWND_MESSAGE);
            NativeMethods.AddClipboardFormatListener(Handle);
        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == NativeMethods.WM_CLIPBOARDUPDATE)
            {
                var contents = Clipboard.GetText();
                var handler = ClipboardUpdate;
                if (handler != null && contents.Length > 0)
                {
                    handler(contents);
                }
            }
            base.WndProc(ref m);
        }
    }
}

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);

    // See http://msdn.microsoft.com/en-us/library/ms633541%28v=vs.85%29.aspx
    // See http://msdn.microsoft.com/en-us/library/ms649033%28VS.85%29.aspx
    [DllImport("user32.dll", SetLastError = true)]
    public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
}