protected abstract void VisitOrElse(OrElseExpression expression);
protected virtual void VisitWhereIn(WhereInExpression expression)
{
IWhereExpression exp = new FalseExpression();
foreach (var value in expression.Values)
{
exp = new OrElseExpression(exp, new WhereEqualsExpression(null, expression.FieldName, value));
}
this.VisitWhere(exp);
}