C# 使用IEqualityComparer接口实现集合对象的动态分组

速度可能有点慢，毕竟使用的是反射。。。

分组效果

 

代码

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

namespace ConsoleApp1
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var list = new List<Student>();
            var stu1 = new Student() { Id = 1, Name = "张三", Age = 18 };
            var stu2 = new Student() { Id = 1, Name = "张三", Age = 18 };
            var stu3 = new Student() { Id = 2, Name = "李四", Age = 18 };
            var stu4 = new Student() { Id = 3, Name = "李四", Age = 18 };
            var stu5 = new Student() { Id = 1, Name = "王五", Age = 18 };
            var stu6 = new Student() { Id = 1, Name = "王五", Age = 18 };
            list.Add(stu1);
            list.Add(stu2);
            list.Add(stu3);
            list.Add(stu4);
            list.Add(stu5);
            list.Add(stu6);

            var refer = new ObjectComparer<Student>(new string[] { "Name", "Id" });
            var groups = list.GroupBy(c => c, refer);
            foreach (var g in groups)
            {
                Console.WriteLine($"key: {g.Key}");
                foreach (var s in g)
                {
                    Console.WriteLine($"    {s.Id}==={s.Name}==={s.Age}");
                }
            }
        }

        private class ObjectComparer<T> : IEqualityComparer<T>
        {
            private PropertyInfo[] _propertyInfos;

            public ObjectComparer(IEnumerable<string> propertyNames)
            {
                var properties = typeof(T).GetProperties();
                var list = new List<PropertyInfo>();
                foreach (var p in properties)
                {
                    if (propertyNames.Contains(p.Name))
                    {
                        list.Add(p);
                    }
                }
                _propertyInfos = list.ToArray();
            }

            public bool Equals(T x, T y)
            {
                foreach (var p in _propertyInfos)
                {
                    var type = p.PropertyType;

                    //使用动态类型，在运行的时候调用对象的Equal方法
                    dynamic value1 = x.GetType().GetProperty(p.Name).GetValue(x);
                    dynamic value2 = y.GetType().GetProperty(p.Name).GetValue(y);
                    if (value1 != value2)
                    {
                        return false;
                    }
                }
                return true;
            }

            public int GetHashCode(T obj)
            {
                var hash = _propertyInfos.Select(p => p.GetValue(obj).GetHashCode())
                                         .Aggregate((x, y) => x & y);
                return hash;
            }
        }

        /// <summary>
        /// 实现了相等性接口
        /// </summary>
        private class Student
        {
            public int Age { get; set; }

            public int Id { get; set; }

            public string Name { get; set; }

            //public bool Equals(Student other)
            //{
            //    if (other == null) { return false; }

            //    if (ReferenceEquals(this, other)) { return true; };

            //    return (Id, Age, Name) == (other.Id, other.Age, other.Name);
            //}

            //public override int GetHashCode()
            //{
            //    return (Id, Age, Name).GetHashCode();
            //}

            //public override string ToString()
            //{
            //    return Name;
            //}
        }
    }
}