目录
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; }
}