.Net 相等性的测试题目，看你基础牢不牢

最新推荐文章于 2021-08-20 17:19:31 发布

weixin_34283445

最新推荐文章于 2021-08-20 17:19:31 发布

阅读量81

点赞数

本文探讨了C#中不同集合类型（如数组、列表、集合及字典）对自定义类实例进行相等性测试的方法。通过逐步完善自定义类People的实现，展示了如何正确实现Equals方法及其相关操作符以确保一致的行为。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

有这么一个简单类People：

    class People
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Id: {0}; Name: {1}", Id, Name);
        }
    }

请看以下代码，给出b0~b6的值（b6的相关代码不熟悉的话，可以只给出b0~b5的值）：

    private static void Test()
    {
        People[] ps0 = new People[]{
            new People{ Id=1, Name = "aaa"},
            new People{ Id=2, Name = "bbb"},
            new People{ Id=3, Name = "ccc"}
        };
        List<People> ps1 = new List<People>(ps0);
        Collection<People> ps2 = new Collection<People>(ps1);
        IEnumerable<People> ps3 = YeildRet(ps0);
        Dictionary<People, string> dict = ps0.ToDictionary(p=>p, p=>p.Name);

        People p0 = new People { Id = 1, Name = "aaa" };

        //
        bool b0 = p0 == ps0[0];
        bool b1 = p0.Equals(ps0[0]);
        //
        bool b2 = ps0.Contains(p0);
        bool b3 = ps1.Contains(p0);
        bool b4 = ps2.Contains(p0);
        bool b5 = ps3.Contains(p0);
        //
        bool b6 = dict.ContainsKey(p0);
    }

    private static IEnumerable<People> YeildRet(People[] peoples)
    {
            yield return peoples[0];
            yield return peoples[1];
            yield return peoples[2];
    }

下面会把People类逐步改进，同样请给出每个版本的b0~b6的值，一个版本一个版本做，做完一个版本才能展开下一个版本。不要作弊奥！

People版本二
    class People
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Id: {0}; Name: {1}", Id, Name);
        }

        public bool Equals(People other)
        {
            return Id.Equals(other.Id);
        }
    }

再改进，

People版本三
    class People: IEquatable<People>
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Id: {0}; Name: {1}", Id, Name);
        }

        public bool Equals(People other)
        {
            return Id.Equals(other.Id);
        }
    }

再改进

People版本四
    class People: IEquatable<People>
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Id: {0}; Name: {1}", Id, Name);
        }

        public bool Equals(People other)
        {
            return Id.Equals(other.Id);
        }

        public override bool Equals(object obj)
        {
            if (obj is People) return Equals((People)obj);
            return base.Equals(obj);
        }
    }

再改进：

People版本五
    class People: IEquatable<People>
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Id: {0}; Name: {1}", Id, Name);
        }

        public bool Equals(People other)
        {
            return Id.Equals(other.Id);
        }

        public override bool Equals(object obj)
        {
            if (obj is People) return Equals((People)obj);
            return base.Equals(obj);
        }

        public static bool operator ==(People left, People right)
        {
            return left.Equals(right);
        }

        public static bool operator !=(People left, People right)
        {
            return !left.Equals(right);
        }

        public override int GetHashCode()
        {
            return Id.GetHashCode();
        }
    }

说明：代码仅供测试用，没有进行null值处理。