Question

使用EF4可以通过属性上的属性进行排序，即

具有Name属性的EntityA。实体B还有一些其他属性和EntityA。我想获得EntityA.Name

订购的EntityB列表

entityBList = _repo.Find<EntityB>() .OrderBy(x => x.EntityA.Name);

Answer 1

为什么这不起作用？我知道它不是使用EF4，但概念是一样的。

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;

    namespace LinqOrderByReference
    {
        class Program
        {
            static void Main(string[] args)
            {
                EntityA[] entitiesA = {   new EntityA { Ordinal = 3, SecretCode = "xxx"}, 
                                          new EntityA { Ordinal = 2 ,SecretCode = "x"}, 
                                          new EntityA { Ordinal = 1 ,SecretCode = "x"} };
                EntityB[] entitiesB = {  new EntityB { Name = "C", EntityA = entitiesA[2] }, 
                                          new EntityB {Name = "B", EntityA = entitiesA[1] },
                                          new EntityB {Name = "A", EntityA = entitiesA[0] } };

                IEnumerable<EntityB> entitiesBList = entitiesB.OrderBy(x => x.EntityA.Ordinal);
                foreach (EntityB b in entitiesBList)
                {
                    Console.WriteLine("EntityB.Name: {0}, Ordinal {1}.", b.Name, b.EntityA.Ordinal);
                }
                Console.Read();
            }
        }

        public class EntityA
        {
            public int Ordinal { get; set; }
            public string SecretCode { get; set; }
        }

        public class EntityB
        {
            public string Name { get; set; }
            public EntityA EntityA { get; set; }
        }
    }

输出是：
EntityB.Name：C，Ordinal 1.
EntityB.Name：B，Ordinal 2.
EntityB.Name：A，Ordinal 3.

Answer 2

name属性是一个简单的字符串，还是包含First name和Last Name，如果是，它会覆盖GetHashCode方法？如果是这样，您可能需要查看此帖子What is the best algorithm for an overridden System.Object.GetHashCode?

对象的linq OrderBy属性

2 个答案: