Question

我刚开始使用nHibernate Fluent，并且我的关联一切顺利，直到我找到一个具有null的StateID（外键，见下文）的位置。然后我收到错误“空引用异常”

此行 Console.WriteLine（location.address +“，”+ location.State.state）;

下面：

public static void LoadLocationsFromDatabase()
{
    using (var session = NHibernateHelper.OpenSession())
    {
        // retreive all stores and display them
        using (session.BeginTransaction())
        {
            var locations = session.CreateCriteria(typeof(Location))
                .List<Location>();

            var i = 0;
            foreach (var location in locations)
            {
                i++;
                Console.WriteLine(location.address + ", " + location.State.state);
            }
        }

    }
}

public LocationMap()
{
    Id(x => x.locationID).Column("ID");
    Map(x => x.address).Column("Address");
    References(x => x.State)
  .Column("StateID")
      .Cascade.All();
}

public class State
{
    public virtual int ID { get; set; }
    public virtual String state { get; set; }
    public virtual IList<Location> Locations { get; set; }
}

我猜这个值在DB中可能不应该为null。 StateID是states表上ID的外键，所以我想不应该允许它为null？

无论如何，我觉得我的代码应该能够允许这种或那种方式，所以我该如何解决这个问题呢？

Answer 1

Console.WriteLine(location.address + ", " + (location.State == null ? "Unknown" : location.State.state));

流利的nhibernate可以为空的外键“空引用异常”

1 个答案: