linq Distinct 去除重复数据-白红宇

linq Distinct 去除重复数据

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发布时间：2019-06-25

本文共 1249 字，大约阅读时间需要 4 分钟。

转载：

只可惜linq默认不支持.Distinct(p => p.ID);

试想如果能写成下面的样子，是不是更简单优雅：

var p1 = products.Distinct(p => p.ID);var p2 = products.Distinct(p => p.Name);

使用一个简单的 lambda 作为参数，也符合 Linq 一贯的风格。

扩展方法：

public static IEnumerable
     
       Distinct
      
       (this IEnumerable
       
         source, Func
        
          keySelector,    IEqualityComparer
         
           comparer = EqualityComparer
          
           .Default){ return source.Distinct(new CommonEqualityComparer
           
            (keySelector, comparer));}

using System;using System.Collections.Generic;using System.Runtime.CompilerServices;using System.Linq;public class CommonEqualityComparer
     
       : IEqualityComparer
      
       {    private Func
       
         keySelector;    private IEqualityComparer
        
          comparer;    public CommonEqualityComparer(Func
         
           keySelector, IEqualityComparer
          
            comparer) { this.keySelector = keySelector; this.comparer = comparer; } public CommonEqualityComparer(Func
           
             keySelector) : this(keySelector, EqualityComparer
            
             .Default) { } public bool Equals(T x, T y) { return comparer.Equals(keySelector(x), keySelector(y)); } public int GetHashCode(T obj) { return comparer.GetHashCode(keySelector(obj)); }}