Question

我有两个类：项目和 DataStructure 。类项目包含成员列表＆lt; DataStructure ＆gt;。我的目标是在一次调用中加载项目及其所有DataStructures。

public class Project
{
    public virtual string Id { get { } set { } }
    public virtual string Name { get { } set { } }
    public virtual ISet<DataStructure> DataStructures { get { } set { } }
}

public class DataStructure
{
    public virtual string Id { get { } set { } }
    public virtual string Name { get { } set { } }
    public virtual string Description { get { } set { } }
    public virtual Project Project { get { } set { } }
    public virtual IList<DataField> Fields { get { } set { } }
}

请注意， DataStructure 还包含类 DataField 的列表，但我不想加载这些现在。

Fluent NHibernate中的映射：

public class ProjectMap : ClassMap<Project>
{
    public ProjectMap()
    {
        Table("PROJECTS");
        Id(x => x.Pk, "PK");
        Map(x => x.Id, "ID");
        Map(x => x.Name, "NAME");
        HasMany<DataStructure>(x => x.DataStructures).KeyColumn("FK_PROJECT");
    }
}

public class DataStructureMap : ClassMap<DataStructure>
{
    public DataStructureMap()
    {
        Table("DATA_STRUCTURES");
        Map(x => x.Id, "ID");
        Map(x => x.Name, "NAME");
        Map(x => x.Description, "DESCRIPTION");
        References<Project>(x => x.Project, "FK_PROJECT");
        HasMany<DataField>(x => x.Fields).KeyColumn("FK_DATA_STRUCTURE");
    }
}

这是我的疑问：

using (ISession session = SessionFactory.OpenSession())
{
    IQuery query = session.CreateQuery("from Project pr left join pr.DataStructure");
    project = query.List<Project>();
}

query.List（）返回此异常：

NHibernate.Exceptions.GenericADOException: Could not execute query[SQL: SQL not available] ---> System.ArgumentException: The value "System.Object[]" is not of type "Project" and cannot be used in this generic collection.

Answer 1

您正在使用的HQL查询同时选择Project和DataStructure（就像常规SQL左连接查询一样）。如果您想要query.List<Project>()，则必须从该查询中投影项目：select pr from Project pr left join pr.DataStructure

Answer 2

是吗？

"select pr from Project pr left join pr.DataStructure"

HQL查询中的ADO异常

2 个答案: