using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;
 
namespace DisablingClipboard
{
    public class Form1 : System.Windows.Forms.Form
    {
        private System.ComponentModel.Container components = null;
 
        const int WM_DRAWCLIPBOARD=0x0308;
        const int WM_CHANGECBCHAIN=0x030D;
        private System.Windows.Forms.CheckBox checkBox1;
        private IntPtr nextviewer;
 
        public Form1()
        {
            InitializeComponent();
        }
 
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if (components != null) 
                {
                    ChangeClipboardChain(this.Handle, nextviewer);
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }
 
        protected void RegisterWindow() 
        {
            nextviewer = SetClipboardViewer(this.Handle);
        }
 
        protected void UnregisterWindow() 
        {
            ChangeClipboardChain(this.Handle, nextviewer);
        }
 
        protected void ClearClipboard() 
        {
            Clipboard.SetDataObject(new DataObject());
        }
 
        protected override void WndProc(ref Message m) 
        {
            switch (m.Msg)
            {
                case WM_CHANGECBCHAIN:
                    if (nextviewer==m.WParam) nextviewer=m.LParam;
                    else SendMessage(nextviewer, 
                             m.Msg, m.WParam, m.LParam);
                    break;
 
                case WM_DRAWCLIPBOARD:
                    ClearClipboard();
 
                    SendMessage(nextviewer, m.Msg, 
                        m.WParam, m.LParam);
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }
 
        #region Windows Form Designer generated code
// ...skipped...
        #endregion
 
        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }
 
        private void checkBox1_CheckedChanged(object sender, 
            System.EventArgs e)
        {
            if (this.checkBox1.Checked) RegisterWindow();
            else UnregisterWindow();
        }
 
        [DllImport("user32.dll")]
        static extern IntPtr SendMessage(IntPtr hWnd, 
            int Msg, IntPtr wParam, IntPtr lParam);
 
        [DllImport("User32.dll")]
        public static extern IntPtr SetClipboardViewer(
            IntPtr hWndNewViewer);
 
        [DllImport("User32.dll")]
        public static extern IntPtr ChangeClipboardChain(
            IntPtr hWndRemove, IntPtr hWndNewNext);
 
    }
}