Goals
Produce compact and comprehensive code using NHibernate QueryOver, Restrictions and ICriterion.
Context
We will take an example with an entity Period, defined by a name, a start date and a end date.
Period
Needs
We want to request database to get periods corresponding some criteria :
- all the periods that contains a date
- all the periods that overlap another period
Implementation
We will use PeriodCriteriaBuilder to build the ICriterion blocks :
Some methods build small criteria :
BuildBeginBeforeOrEqualCriterion(DateTime date)BuildEndAfterOrEqualCriterion(DateTime date)BuildBeginBetweenCriterion(DateTime start, DateTime end)BuildEndBetweenCriterion(DateTime start, DateTime end)
Then we can combine them with logical Restrictions expression to provide more advanced predicates :
BuildBeginOrEndBetweenCriterion(DateTime start, DateTime end)BuildContainsDateCriterion(DateTime date)BuildContainsStartOrEndDateCriterion(DateTime start, DateTime end)BuildOverlapsPeriodCriterion(DateTime start, DateTime end)