NHibernate的QueryOver分頁雖然選擇車篷1子查詢

Question

我有2個實體（這些被分解到的問題要簡單一些）：

實體A

public class EntityA 
     { 
      protected IList<EntityB> _bList = new List<EntityB>(); 

      virtual public int Id { get; set; } 
      virtual public int ExtId { get; set; } 


      public virtual void AddB(EntityB b) 
      { 
       if (!_bList.Contains(b)) _bList.Add(b); 
       b.A = this; 
       b.ExtId = this.ExtId; 
      } 

      public virtual void RemoveB(EntityB b) 
      { 
       _bList.Remove(b); 
      } 

      public virtual IList<EntityB> BList 
      { 
       get { return _bList.ToList().AsReadOnly(); } 
      } 
     } 

實體的映射

<?xml version="1.0" encoding="utf-8" ?> 
    <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="true"> 
     <class name="hibernate.domain.mappings.EntityA, hibernate.domain" lazy="true"> 
     <id name="Id"> 
      <generator class="native" /> 
     </id> 
     <property type="int" name="ExtId" column="[ExtId]" /> 
     <bag 
      name="BList" 
      table="EntityB" 
      cascade="all" 
      lazy="true" 
      inverse="true" 
      access="field.camelcase-underscore" 
      optimistic-lock="false" 
      > 
      <key column ="ExtId" property-ref="ExtId" /> 
      <one-to-many class="hibernate.domain.mappings.EntityB, hibernate.domain" /> 
     </bag> 
    </hibernate-mapping> 

實體B

 public class EntityB 
     { 
      protected EntityA _a; 

      virtual public int Id { get; set; } 
      virtual public int ExtId { get; set; } 
      virtual public EntityA A 
      { 
       get { return _a; } 
       set { _a = value; } 
      } 
     } 

實體B映射

<?xml version="1.0" encoding="utf-8" ?> 
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="true"> 
    <class name="hibernate.domain.mappings.EntityB, hibernate.domain" lazy="true"> 
    <id name="Id"> 
     <generator class="native" /> 
    </id> 
    <property type="int" name="ExtId" column="[EXTID]" /> 
    <many-to-one 
      name = "A" 
     property-ref ="ExtId" 
      not-null="true" 
      class = "hibernate.domain.mappings.EntityA, hibernate.domain" 
     access="field.camelcase-underscore" 
      cascade = "save-update" 
      fetch="select" 
      insert = "false" 
     lazy = "false" 
      update = "false" 
     column="ExtId" 
     /> 
    </class> 
</hibernate-mapping> 

我需要做的是使用Queryover分頁得到一個清單，而選擇與A相關的B的第一項，

我用以下queryover，

using (ISession session = SessionProvider.OpenSession()) 
       { 
        var bOver = (QueryOver<EntityB, EntityB>)session.QueryOver(() => bAlias) 
         .JoinAlias(() => bAlias.A,() => aAlias) 
         .SelectList(b => b.Select(() => bAlias.Id)) 
         .Take(1); 

        var aOver = session.QueryOver(() => aAlias) 
         .SelectList(l => l.Select(() => aAlias.Id) 
         .SelectSubQuery<EntityB>(bOver)); 



var result = aOver.Skip(1).Take(1).List<object[]>(); 
      } 

但是所生成的查詢等，以下

SELECT TOP (10) y0_, 
       (SELECT TOP (10) this_0_.id AS y0_ 
       FROM (SELECT this_.id 
           AS y0_, 
           (SELECT TOP (1) this_0_.id 
               AS 
               y0_, 
               Row_number() OVER(ORDER BY 
               current_timestamp) AS 
               __hibernate_sort_row 
           FROM entityb this_0_ 
             INNER JOIN entitya aalias1_ 
              ON 
this_0_.extid = aalias1_.[EXTID]) 
AS y1_ 
FROM entitya this_) AS QUERY 
WHERE QUERY.__hibernate_sort_row > 1 
ORDER BY QUERY.__hibernate_sort_row) 

這是不正確的，那麼我該如何解決這種情況（在現實世界的情況下，我需要選擇多個第一項，如B與A）

Answer 1

好吧，我設法解決了這種情況小劈NHibernate的預測（實際上添加一個自定義）

[Serializable] 
    public class TopRowProjection : SimpleProjection 
    { 
     private PropertyProjection _projection; 

     public TopRowProjection(PropertyProjection projection) 
     { 
      _projection = projection; 
     } 

     public override bool IsAggregate 
     { 
      get { return true; } 
     } 

     public override IType[] GetTypes(ICriteria criteria, ICriteriaQuery criteriaQuery) 
     { 
      return _projection.GetTypes(criteria, criteriaQuery); 
     } 

     public override SqlString ToSqlString(ICriteria criteria, int position, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters) 
     { 
      SqlStringBuilder result = new SqlStringBuilder().Add(" top(1) "); 
      result.Add(_projection.ToSqlString(criteria, position, criteriaQuery, enabledFilters)); 
      result.Add(" "); 
      return result.ToSqlString(); 
     } 

     public override string ToString() 
     { 
      return "select top(1)"; 
     } 

     public override bool IsGrouped 
     { 
      get { return false; } 
     } 

     public override SqlString ToGroupSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, 
                IDictionary<string, IFilter> enabledFilters) 
     { 
      throw new InvalidOperationException("not a grouping projection"); 
     } 
    } 

和代碼修改如下，和所有制定了罰款

using (ISession session = SessionProvider.OpenSession()) 
      { 
       var bOver = (QueryOver<EntityB, EntityB>)session.QueryOver(() => bAlias) 
        .JoinAlias(() => bAlias.A,() => aAlias) 
        .Select(new TopRowProjection(Projections.Property(() => bAlias.Id))); 

       var aOver = session.QueryOver(() => aAlias) 
        .SelectList(l => l.Select(() => aAlias.Id) 
        .SelectSubQuery<EntityB>(bOver)); 

       var result = aOver.Skip(1).Take(1).List<object[]>(); 
      }