Question

我如何在NHibernate中表达这一点？

DECLARE @EntityId INT = 800;

SELECT *
FROM UserAlert
WHERE UserAlertId =  
                  (
                   SELECT MAX(UserAlertId)
                   FROM UserAlert
                   WHERE EntityId = @EntityId
                  )

这就是我想要做的。

var senderUA = session.CreateCriteria<UserAlert>()
                      .Add(Restrictions.Eq("EntityId", id))
                      .SetProjection( Projections.Max("Id") )
                      . UniqueResult();

我一直收到一个可以将对象转换为UserAlert类型的错误，即它甚至没有编译。

感谢您的帮助

Answer 1

按UserAlertId排序并选择前1名会更简单。

var senderUA = session.CreateCriteria<UserAlert>()
                  .Add(Restrictions.Eq("EntityId", id))
                  .AddOrder(Order.Desc("UserAlertId"))
                  .SetMaxResults(1)
                  .UniqueResult();

另外你可以

var senderUA = session
                    .Query<UserAlert>()
                    .Where(x=>x.EntityId==id && 
                         x.UserAlertId==session.Query<UserAlert>()
                                           .Where(x=>x.EntiryId==id).Max(x=>x.UserAlertId)
                          ).FirstOrDefault();

Answer 2

以下是使用QueryOver的解决方案。

var maxUserAlertId = QueryOver.Of<UserAlert>
                             .Where(ua => ua.EntityId == id)
                             .Select(
                                 Projections.Max(
                                    Projections.Property<UserAlert>
                                                      (u => u.UserAlertId)
                                 )
                               );
var maxUserQuery = session
                     .QueryOver<UserAlert>()
                     .WithSubquery
                         .WhereProperty(u => u.EntityId)
                         .Eq(maxUserAlertId);

// Dealing with the situation that the maximum value is shared
// by more than one row. If you're certain that it can only
// be one, call SingleOrDefault instead of List
IList<UserAlert> results = maxUserQuery.List();

NHibernate中的where子句

2 个答案: