public override bool Equals(object obj)
        {
            if (obj == null)
            {
                return(false);
            }

            SQLiteNullExpression dst = obj as SQLiteNullExpression;

            if (dst == null)
            {
                return(false);
            }

            return(true);
        }
        public override object Clone()
        {
            SQLiteExpression res = new SQLiteNullExpression();

            return(res);
        }