using System; using System.Windows.Forms; public class BlockLeftMouseButtonMessageFilter : IMessageFilter { const int WM_LBUTTONDOWN = 0x201; public bool PreFilterMessage(ref Message m){ if(m.Msg == WM_LBUTTONDOWN) { Console.WriteLine("The left mouse button is down."); Application.RemoveMessageFilter(this); return true; } return false; } } public class MainForm : Form { public static void Main() { MainForm MyForm = new MainForm(); BlockLeftMouseButtonMessageFilter MsgFilter = new BlockLeftMouseButtonMessageFilter(); Application.AddMessageFilter(MsgFilter); Application.Run(MyForm); } public MainForm() { Text = "Message Filter Removal Test"; } }