将Nhibernate查询转换为通用列表时出错

Question

我叫一个简单的实体EmployeeEntity与性质ID,Name,Age,Organisation,和Designation.我只是使用查询查询数据库

IQuery query = session.CreateQuery(
    "select Name, Designation, Age, Organisation FROM EmployeeEntity " +
    "group by Name, Designation, Age, Organisation");

IList<EmployeeEntity> employee = query.List<EmployeeEntity>(); // Throws error

但在转换为我的类型时,它会抛出异常:

无法执行查询[SQL:SQL不可用]

用InnerException:

值"System.Object []"不是"NHibernateTest.EmployeeEntity"类型,不能在此通用集合中使用.
参数名称:value

虽然它使用此查询工作正常:

IQuery query = session.CreateQuery("select e FROM EmployeeEntity e group by e");

IList<EmployeeEntity> employee = query.List<EmployeeEntity>();

但我不想选择所有列,因为我不需要它们.

Answer 1

如果您只需要某组列,请创建一个与您的列一对一映射的类.像这样:

public class EmployeeView
{
    public string Name { get; set; }
    public string Designation { get; set; }
    public int Age { get; set; }
    public string Organization { get; set; }
}

然后,您只需要在查询中添加结果转换器

IQuery query = session
    .CreateQuery("select Name ,Designation ,Age ,Organisation  FROM EmployeeEntity   group by  Name ,Designation ,Age ,Organisation")
    .SetResultTransformer(Transformers.AliasToBean<EmployeeView>());

Ilist<EmployeeEntity> employee= query.List<EmployeeView>();

Answer 2

当你查询时select Name, Designation, Age, Organisation...,NHibernate实际上将返回一个IList<object[]>实例.要解决此问题,请尝试重写HQL select new EmployeeEntity(Name, Designation, Age, Organisation)...并向EmployeeEntity类添加适当的构造函数.