//**************************************************************
        // InitializeKeyCheck()
        //**************************************************************
        public void InitializeKeyCheck()
        {
            //Clear any previous app domain
            UnInitializeKeyCheck();

            AD = AppDomain.CreateDomain("KeyValidatorDomain");

            BindingFlags flags = (BindingFlags.Public | BindingFlags.Instance | BindingFlags.CreateInstance);

            ObjectHandle objh = AD.CreateInstance( "AppUpdater", "Microsoft.Samples.AppUpdater.KeyValidator", false,
                               flags, null, null, null, null, null);

            // Unwrap the object
            Object obj = objh.Unwrap();

            // Cast to the actual type
            Validator = (KeyValidator)obj;

            KeyList = GetKeyList(AppUrl.TrimEnd(new char[] {'/'}) + "/" + KEYFILENAME);
        }