Question

我正在粘贴下面的代码;

我的基类重写了Equals和getHashcode，但是linq查询没有返回不同的结果。结果中有多个城市具有相同的ID。

public class Product : EntityBase
   {
        public virtual string Name { get; set; }

        public virtual IList<ProductDayDefinition> Days { get; set; }
   }

   public class ProductDayDefinition : EntityBase
   {
        public virtual Product Product { get; set; }

        public virtual City City { get; set; }

    }


public abstract class EntityBase
    {
        public virtual int ID { get; protected internal set; }

        protected EntityBase() : this(0) 
        { 

        }

        protected EntityBase(int ID)
        {
            this.ID = ID;

            if (this.ID == null)
                this.ID = 0;
        }           

        #region Equals definitions
        public override bool Equals(object entity)
        {
            return entity != null
                && entity is EntityBase
                && this == (EntityBase)entity;
        }

        public static bool operator ==(EntityBase base1, EntityBase base2)
        {
            if ((object)base1 == null && (object)base2 == null)
                return true;

            if ((object)base1 == null || (object)base2 == null)
                return false;

            if (base1.ID != base2.ID)
                return false;

            return true;
        }

        public static bool operator !=(EntityBase base1, EntityBase base2)
        {
            return (!(base1 == base2));
        }

        public override int GetHashCode()
        {
            return this.ID.GetHashCode();
        }
        #endregion
    }

var cities = (from product in NHibernateSession.Linq<Product>() 
              from day in product.Days
              where day.City != null
              select day).Distinct();

Answer 1

查询在服务器端执行（在数据库中）。重写equals或gethashcode没有任何区别。

只需选择id属性，然后在最后调用Distinct。您将不得不迭代结果以获取更多信息。

OR

您可以使用联接来获取从子查询返回的ID的详细信息。

http://msdn.microsoft.com/en-us/library/cc716801.aspx

linq明显没有给出明显的结果

1 个答案: