c# - 在单个列表中获取重复的字段名称

Question

我有一个 List<Car> lstcar具有属性

name-Zen id-1211 MfYear-1990 Color-black
name-Alto id-1521 MfYear-1990 Color-black
name-Nano id-9911 MfYear-1990 Color-black
name-800 id-1721 MfYear-1990 Color-black
name-zen id-711 MfYear-1990 Color-black
name-Swift id-9911 MfYear-1990 Color-black
name-Nano id-1081 MfYear-1990 Color-black

我想要基于名称的重复项的名称 例如:我想要“Zen , Nano”，但是当我这样做的时候

   List<Car> dup = lstcar.GroupBy(s => s.CarName)
         .Select(grp => grp.FirstOrDefault())
         .OrderBy(s => s.CarName)
         .ToList<Car>();

我得到 dup有这个值

name-Zen id-1211 MfYear-1990 Color-black
name-Alto id-1521 MfYear-1990 Color-black
name-Nano id-9911 MfYear-1990 Color-black
name-800 id-1721 MfYear-1990 Color-black     
name-Swift id-9911 MfYear-1990 Color-black

但是我想要

 name-Zen id-1211 MfYear-1990 Color-black     
 name-Nano id-9911 MfYear-1990 Color-black    
 name-zen id-711 MfYear-1990 Color-black   
 name-Nano id-1081 MfYear-1990 Color-black

如何从一个 List<T> 中获取重复项？

Answer 1

添加 Where 子句以仅获取包含超过 1 个元素的组和 SelectMany 以将结果展平到一个列表中:

var duplications = lstcar.GroupBy(s => s.CarName)
                         .Where(g => g.Count() > 1)
                         .SelectMany(g => g)
                         .ToList();

我看到你不会在同一组中Zen和zen，所以你应该将你的GroupBy更改为:GroupBy (s => s.CarName.ToLower())