[ComVisible(true), Guid("C59D3771-0E3E-48B8-97C5-9CD2C091CF09"), ClassInterface(ClassInterfaceType.None)]
    public class BHO : IObjectwithsite
    {
        public int SetSite(object site)
        {
            return 0;
        }

        public int GetSite(ref Guid guid, out IntPtr ppvSite)
        {
            IntPtr punk = Marshal.GetIUnknownForObject(IPCServer.WebBrowser);
            int hr = Marshal.QueryInterface(punk, ref guid, out ppvSite);
            Marshal.Release(punk);
            return hr;
        }

        #region RegisterBHO

        public static string BHOKEYNAME = "Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Browser Helper Objects";  

        [ComRegisterFunction]  
        public static void RegisterBHO(Type type)  
        {
            RegistryKey registryKey = Registry.LocalMachine.OpenSubKey(BHOKEYNAME, true);  
 
            if (registryKey == null)  
                registryKey = Registry.LocalMachine.CreateSubKey(BHOKEYNAME);  
 
            string guid = type.GUID.ToString("B");  
            RegistryKey ourKey = registryKey.OpenSubKey(guid);  
  
            if (ourKey == null)  
                ourKey = registryKey.CreateSubKey(guid);  
  
            registryKey.Close();  
            ourKey.Close();  
        }  
  
        [ComUnregisterFunction]  
        public static void UnregisterBHO(Type type)  
        {  
            RegistryKey registryKey = Registry.LocalMachine.OpenSubKey(BHOKEYNAME, true);  
            string guid = type.GUID.ToString("B");  
  
            if (registryKey != null)  
                registryKey.DeleteSubKey(guid, false);
        }

        #endregion
    }