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C#使用Linq實現(xiàn)簡單去重處理

更新時間：2025年02月20日 08:40:46 作者：我是蘇蘇

這篇文章主要為大家詳細(xì)介紹了C#如何使用Linq實現(xiàn)簡單去重處理功能,文中的示例代碼講解詳細(xì),感興趣的小伙伴可以跟隨小編一起學(xué)習(xí)一下

一、示例代碼

using System;
using System.Collections.Generic;
using System.Linq;
 
public class Program
{
    public static void Main()
    {
        // 創(chuàng)建一些示例實體對象
        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" },//重復(fù)的
            new Person { Name = "Charlie", Age = 35, City = "Chicago" },
            new Person { Name = "Alice", Age = 28, City = "San Francisco" }
        };
 
        // 1. 單字段去重
        var uniqueNameFields = people.DistinctBy(p =>p.Name).ToList();
        Console.WriteLine("指定字段（Name）去重結(jié)果,重復(fù)則保留第一條:");
        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）去重結(jié)果,重復(fù)則保留第一條:");
        foreach (var person in uniqueNameAgeFields)
        {
            Console.WriteLine($"Name: {person.Name}, Age: {person.Age}, City: {person.City}");
        }
 
        //3.全字段去重
        // 通過 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、示例輸出

指定字段（Name）去重結(jié)果,重復(fù)則保留第一條:
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）去重結(jié)果,重復(fù)則保留第一條:
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、注意雷點

以下代碼不能完成全字段去重，因為people是引用類型，Distinct() 一般用于List<string>,List<int>這些值類型去重，而不涉及引用類型的字段比較。

people.Distinct().ToList()

若需要全字段去重：1.使用DinstinctBy語法，加上所有字段。2.使用標(biāo)題四的封裝方法（反射實現(xiàn)全字段去重）。

四、全字段去重封裝方法

1.封裝

/// <summary>
/// 通用的全字段去重方法
/// </summary>
/// <returns></returns>
public static IEnumerable<T> DistinctByAllFields<T>(IEnumerable<T> items)
{
    // 獲取 T 類型的所有字段值
    var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
 
    return items
        .GroupBy(item => string.Join(",", properties.Select(p => p.GetValue(item))))  // 按所有字段值連接生成唯一標(biāo)識符
        .Select(group => group.First());  // 取每組的第一個元素
}

2.示例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
 
public class Program
{
    public static void Main()
    {
        // 創(chuàng)建一些示例實體對象
        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" }
        };
 
        // 調(diào)用封裝的去重方法
        var uniquePeople = DistinctByAllFields(people).ToList();
 
        Console.WriteLine("根據(jù)所有字段去重的結(jié)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)
    {
        // 獲取 T 類型的所有字段值
        var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
 
        return items
            .GroupBy(item => string.Join(",", properties.Select(p => p.GetValue(item))))  // 按所有字段值連接生成唯一標(biāo)識符
            .Select(group => group.First());  // 取每組的第一個元素
    }
}
 
public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
    public string City { get; set; }
}

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