C#基础：使用Linq进行简单去重处理（DinstinctBy/反射）

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

---

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; }
}