鹤岗哈尔滨网站建设长沙网络营销学校

目录

一、示例代码

二、示例输出

三、注意雷点

四、全字段去重封装方法

1.封装

2.示例

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一、示例代码

using System;
using System.Collections.Generic;
using System.Linq;public class Program
{public static void Main(){// 创建一些示例实体对象var people = new List<Person>{new Person { Name = "Alice", Age = 30, City = "New York" },new Person { Name = "Bob", Age = 25, City = "Los Angeles" },new Person { Name = "Alice", Age = 30, City = "New York" },//重复的new Person { Name = "Charlie", Age = 35, City = "Chicago" },new Person { Name = "Alice", Age = 28, City = "San Francisco" }};// 1. 单字段去重var uniqueNameFields = people.DistinctBy(p =>p.Name).ToList();Console.WriteLine("指定字段（Name）去重结果,重复则保留第一条:");foreach (var person in uniqueNameFields){Console.WriteLine($"Name: {person.Name}, Age: {person.Age}, City: {person.City}");}// 2. 多字段去重var uniqueNameAgeFields = people.DistinctBy(p => new { p.Name, p.Age }).ToList();Console.WriteLine("\n指定字段（Name, Age）去重结果,重复则保留第一条:");foreach (var person in uniqueNameAgeFields){Console.WriteLine($"Name: {person.Name}, Age: {person.Age}, City: {person.City}");}//3.全字段去重// 通过 GroupBy 按 Name 和 Age 字段去重var uniquePeople = people.DistinctBy(p => new { p.Name, p.Age, p.City }).ToList();Console.WriteLine("\n全字段去重:");foreach (var person in uniquePeople){Console.WriteLine($"Name: {person.Name}, Age: {person.Age}, City: {person.City}");}}
}public class Person
{public string Name { get; set; }public int Age { get; set; }public string City { get; set; }
}

二、示例输出

指定字段（Name）去重结果,重复则保留第一条:
Name: Alice, Age: 30, City: New York
Name: Bob, Age: 25, City: Los Angeles
Name: Charlie, Age: 35, City: Chicago指定字段（Name, Age）去重结果,重复则保留第一条:
Name: Alice, Age: 30, City: New York
Name: Bob, Age: 25, City: Los Angeles
Name: Charlie, Age: 35, City: Chicago
Name: Alice, Age: 28, City: San Francisco全字段去重:
Name: Alice, Age: 30, City: New York
Name: Bob, Age: 25, City: Los Angeles
Name: Charlie, Age: 35, City: Chicago
Name: Alice, Age: 28, City: San Francisco

三、注意雷点

        以下代码不能完成全字段去重，因为people是引用类型，Distinct() 一般用于List<string>,List<int>这些值类型去重，而不涉及引用类型的字段比较。

people.Distinct().ToList()

        若需要全字段去重：1.使用DinstinctBy语法，加上所有字段。2.使用标题四的封装方法（反射实现全字段去重）。

四、全字段去重封装方法

1.封装

/// <summary>
/// 通用的全字段去重方法
/// </summary>
/// <returns></returns>
public static IEnumerable<T> DistinctByAllFields<T>(IEnumerable<T> items)
{// 获取 T 类型的所有字段值var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);return items.GroupBy(item => string.Join(",", properties.Select(p => p.GetValue(item))))  // 按所有字段值连接生成唯一标识符.Select(group => group.First());  // 取每组的第一个元素
}

2.示例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;public class Program
{public static void Main(){// 创建一些示例实体对象var people = new List<Person>{new Person { Name = "Alice", Age = 30, City = "New York" },new Person { Name = "Bob", Age = 25, City = "Los Angeles" },new Person { Name = "Alice", Age = 30, City = "New York" },new Person { Name = "Charlie", Age = 35, City = "Chicago" },new Person { Name = "Alice", Age = 28, City = "San Francisco" }};// 调用封装的去重方法var uniquePeople = DistinctByAllFields(people).ToList();Console.WriteLine("根据所有字段去重的结果:");foreach (var person in uniquePeople){Console.WriteLine($"Name: {person.Name}, Age: {person.Age}, City: {person.City}");}}/// <summary>/// 通用的全字段去重方法/// </summary>/// <returns></returns>public static IEnumerable<T> DistinctByAllFields<T>(IEnumerable<T> items){// 获取 T 类型的所有字段值var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);return items.GroupBy(item => string.Join(",", properties.Select(p => p.GetValue(item))))  // 按所有字段值连接生成唯一标识符.Select(group => group.First());  // 取每组的第一个元素}
}public class Person
{public string Name { get; set; }public int Age { get; set; }public string City { get; set; }
}