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这些都是我的实体（简化）：NHibernate的查询问题
public class IdentificationRequest
{
private int id;
private ICollection<IdentificationRequestStateHistoryItem> stateHistoryItems;
public virtual string Id
{
get { return id; }
private set { id = value; }
}
public virtual IEnumerable<IdentificationRequestStateHistoryItem> StateHistoryItems
{
get { return stateHistoryItems; }
private set { stateHistoryItems = new List<IdentificationRequestStateHistoryItem>(value); }
}
public void ChangeState(IdentificationRequestState state)
{
// state transition here
var stateHistoryItem = new IdentificationRequestStateHistoryItem(state, this);
stateHistoryItems.Add(stateHistoryItem);
}
}
public class IdentificationRequestStateHistoryItem
{
private int id;
private IdentificationRequestState state;
private EntityTimestamp timestamp;
public virtual string Id
{
get { return id; }
private set { id = value; }
}
public virtual IdentificationRequestState State
{
get { return state; }
private set { state = value; }
}
public virtual EntityTimestamp Timestamp
{
get { return timestamp; }
private set { timestamp = value; }
}
}
public class IdentificationRequestState
{
// possible states are
// Received, then id = 10
// Finished, then id = 20
private int id;
private string name;
public virtual string Name
{
get { return name; }
private set { name = value; }
}
public virtual string Id
{
get { return id; }
private set { id = value; }
}
}
public class EntityTimestamp
{
private DateTime createdOn;
public virtual DateTime CreatedOn
{
get { return createdOn; }
private set { createdOn = value; }
}
private IUser createdBy;
public virtual IUser CreatedBy
{
get { return createdBy; }
private set { createdBy = value; }
}
private DateTime changedOn;
public virtual DateTime ChangedOn
{
get { return changedOn; }
private set { changedOn = value; }
}
private IUser changedBy;
public virtual IUser ChangedBy
{
get { return changedBy; }
private set { changedBy = value; }
}
}
所以上面读起来就像下面并设计一样，在数据库中。
一个IdentificationRequest可以跟踪其IdentificationRequestState转换。因此，每次分配新的IdentificationRequestState时，都会创建一个新的IdentificationRequestStateHistoryItem，并将其放入多个历史记录项目的集合中。这意味着，当前IdentificationRequestState是最后一个添加的（由createdOn日期表示）。
所以，现在我的问题是，查询的样子，列出所有IdentificationRequest的whos当前状态是收到，或完成。
这是我走到这一步：
private ICollection<IdentificationRequest> GetByCurrentState(IdentificationRequestState state)
{
var session = GetCurrentSession();
var subCriteria = DetachedCriteria.For(typeof(IdentificationRequestStateHistoryItem))
.SetProjection(Projections.Property("identificationRequest.Id"));
subCriteria.Add(Restrictions.Eq("State", state));
var criteria = session
.CreateCriteria(typeof (IdentificationRequest))
.Add(Subqueries.PropertyIn("Id", subCriteria))
.SetResultTransformer(new NHibernate.Transform.DistinctRootEntityResultTransformer());
return criteria.List<IdentificationRequest>();
}
但是使用这个查询时，并寻求其当前状态标识请求收到时，我也得请求以来的要求有其当前的状态下结束之前收到的状态。所以我需要用Max（CreatedOn）做些什么...？
NHibernate的映射：
<class name="IdentificationRequest" table="IdentificationRequest">
<id name="Id" column="IdentificationRequestId" unsaved-value="-1">
<generator class="identity"/>
</id>
<bag name="stateHistoryItems" access="field" order-by="CreatedOn desc" fetch="join" cascade="all-delete-orphan" lazy="false">
<key column="IdentificationRequestId"/>
<one-to-many class="IdentificationRequestStateHistoryItem"/>
</bag>
</class>
<class name="IdentificationRequestStateHistoryItem" table="IdentificationRequestStateHistoryItem">
<id name="Id" column="IdentificationRequestStateHistoryItemId" unsaved-value="-1">
<generator class="identity"/>
</id>
<many-to-one name="identificationRequest" access="field" lazy="false" cascade="none" column="IdentificationRequestId" class="IdentificationRequest"></many-to-one>
<many-to-one name="State" lazy="false" fetch="join" cascade="none" column="IdentificationRequestStateId" class="IdentificationRequestState"></many-to-one>
<component name="Timestamp" class="EntityTimestamp">
<property name="CreatedOn"/>
<component name="CreatedBy" class="User">
<property name="Name" column="CreatedBy" />
</component>
<property name="ChangedOn"/>
<component name="ChangedBy" class="User">
<property name="Name" column="ChangedBy" />
</component>
</component>
</class>
<class name="IdentificationRequestState" table="IdentificationRequestState">
<id name="Id" column="IdentificationRequestStateId" unsaved-value="-1">
<generator class="assigned"/>
</id>
<property name="Name"/>
</class>