MouseWheelRedirector.cs

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;

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

public class MouseWheelRedirector : IMessageFilter
{

	private static MouseWheelRedirector instance = null;

	private static bool _active = false;
	public static bool Active {
		get { return _active; }
		set {
			if (_active != value) {
				_active = value;
				if (_active) {
					if (instance == null) {
						instance = new MouseWheelRedirector();
					}
					Application.AddMessageFilter(instance);
				} else {
					if (instance != null) {
						Application.RemoveMessageFilter(instance);
					}
				}
			}
		}
	}

	public static void Attach(Control control)
	{
		if (!_active)
			Active = true;
		control.MouseEnter += instance.ControlMouseEnter;
		control.MouseLeave += instance.ControlMouseLeaveOrDisposed;
		control.Disposed += instance.ControlMouseLeaveOrDisposed;
	}

	public static void Detach(Control control)
	{
		if (instance == null)
			return;
		control.MouseEnter -= instance.ControlMouseEnter;
		control.MouseLeave -= instance.ControlMouseLeaveOrDisposed;
		control.Disposed -= instance.ControlMouseLeaveOrDisposed;
		if (object.ReferenceEquals(instance.currentControl, control))
			instance.currentControl = null;
	}

	private MouseWheelRedirector()
	{
	}


	private Control currentControl;
	private void ControlMouseEnter(object sender, System.EventArgs e)
	{
		var control = (Control)sender;
		if (!control.Focused) {
			currentControl = control;
		} else {
			currentControl = null;
		}
	}

	private void ControlMouseLeaveOrDisposed(object sender, System.EventArgs e)
	{
		if (object.ReferenceEquals(currentControl, sender)) {
			currentControl = null;
		}
	}

	private const int WM_MOUSEWHEEL = 0x20a;
	public bool PreFilterMessage(ref System.Windows.Forms.Message m)
	{
		if (currentControl != null && m.Msg == WM_MOUSEWHEEL) {
			SendMessage(currentControl.Handle, m.Msg, m.WParam, m.LParam);
			return true;
		} else {
			return false;
		}
	}

	[DllImport("user32.dll", SetLastError = false)]
	private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);

}