public static string GetOpName(this QueryJoinOperator op)
        {
            switch (op)
            {
            case QueryJoinOperator.eq: return("=");

            case QueryJoinOperator.ne: return("<>");

            case QueryJoinOperator.le: return("<=");

            case QueryJoinOperator.ge: return(">=");

            case QueryJoinOperator.lt: return("<");

            case QueryJoinOperator.gt: return(">");
            }
            throw new Exception();
        }
 public void SwitchOpLt()
 {
     m_operator = QueryJoinOperator.lt;
     Invalidate();
 }
 public void SwitchOpGe()
 {
     m_operator = QueryJoinOperator.ge;
     Invalidate();
 }
 public void SwitchOpEq()
 {
     m_operator = QueryJoinOperator.eq;
     Invalidate();
 }