Question

我有非常简单的linq表达式：

session.Query<Order>().Where(x => x.States.OrderByDescending(z => z.Date).FirstOrDefault().Name == "2").ToList();

结果：InvalidCastException无法将类型为“Antlr.Runtime.Tree.CommonTree”的对象强制转换为“NHibernate.Hql.Ast.ANTLR.Tree.IASTNode”。

LinqPad的相同查询按预期工作：选择订单，最后一个状态是OnTheWay。我怎样才能绕过这个并获得理想的结果呢？

尝试自己的代码：

class Program
    {
        static void Main(string[] args)
        {
            ISessionFactory sessionFactory = Fluently.Configure()
                .Database(MsSqlConfiguration.MsSql2008
                              .ConnectionString(x => x.FromConnectionStringWithKey("defaultConnectionStringForNhibernate")))
                .Mappings(m => m.FluentMappings.AddFromAssembly(Assembly.GetEntryAssembly()))
                .BuildSessionFactory();
            var session = sessionFactory.OpenSession();
            var res2 =
                session.Query<Order>().Where(x => x.States.OrderByDescending(z => z.Date).FirstOrDefault().Name == "2").ToList();
        }
    }

public class Order
{
    public virtual int Id { get; set; }
    public virtual IList<OrderState> States { get; set; }
    public virtual string Name { get; set; }
}
public class OrderState
{
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual DateTime Date { get; set; }
    public virtual Order Order { get; set; }
}

public class OrderMap : ClassMap<Order>
{
    public OrderMap()
    {
        Id(x => x.Id)
            .GeneratedBy.Identity();
        HasMany(x => x.States)
            .Inverse()
            .AsBag()
            .KeyColumn("OrderId");
        Map(x => x.Name)
            .Not.Nullable();
        Table("Orders");
    }
}
public class OrderStateMap : ClassMap<OrderState>
{
    public OrderStateMap()
    {
        Id(x => x.Id)
            .GeneratedBy.Identity();
        References(x => x.Order)
            .Column("OrderId");
        Map(x => x.Name)
            .Not.Nullable();
        Map(x => x.Date)
            .Not.Nullable();
        Table("OrderStates");
    }
}

Answer 1

经过一段时间的研究后，我找到了解决方案：

var res = (from i in session.Query<Order>()
                      where ((from s in i.States
                              orderby s.Date descending
                              select s.Name).First()) == "2"
                      select i).ToList();

当按相关表查找时，NHibernate查询抛出异常

1 个答案: