C#使用Linq实现简单去重处理
作者:我是苏苏
这篇文章主要为大家详细介绍了C#如何使用Linq实现简单去重处理功能,文中的示例代码讲解详细,感兴趣的小伙伴可以跟随小编一起学习一下
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; } }
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