linq - 合并2个列表并删除重复项。在第三个列表中输出。我的尝试不起作用

当我需要比较2个列表并生成包含所有唯一项的第3个列表时，我似乎总是遇到问题。我需要经常执行此操作。

尝试通过一个带有点头的例子来重现该问题。

我想念什么吗？
谢谢你的建议

所需结果

   Name= Jo1 Surname= Bloggs1 Category= Account
   Name= Jo2 Surname= Bloggs2 Category= Sales
   Name= Jo5 Surname= Bloggs5 Category= Development
   Name= Jo6 Surname= Bloggs6 Category= Management
   Name= Jo8 Surname= Bloggs8 Category= HR
   Name= Jo7 Surname= Bloggs7 Category= Cleaning

class Program
{
    static void Main(string[] args)
    {
          List<Customer> listOne = new List<Customer>();
        List<Customer> listTwo = new List<Customer>();

        listOne.Add(new Customer { Category = "Account", Name = "Jo1", Surname = "Bloggs1" });
        listOne.Add(new Customer { Category = "Sales", Name = "Jo2", Surname = "Bloggs2" });
        listOne.Add(new Customer { Category = "Development", Name = "Jo5", Surname = "Bloggs5" });
        listOne.Add(new Customer { Category = "Management", Name = "Jo6", Surname = "Bloggs6" });



        listTwo.Add(new Customer { Category = "HR", Name = "Jo8", Surname = "Bloggs8" });
        listTwo.Add(new Customer { Category = "Sales", Name = "Jo2", Surname = "Bloggs2" });
        listTwo.Add(new Customer { Category = "Management", Name = "Jo6", Surname = "Bloggs6" });
        listTwo.Add(new Customer { Category = "Development", Name = "Jo5", Surname = "Bloggs5" });
        listTwo.Add(new Customer { Category = "Cleaning", Name = "Jo7", Surname = "Bloggs7" });


    List<Customer> resultList = listOne.Union(listTwo).ToList();//**I get duplicates why????**

        resultList.ForEach(customer => Console.WriteLine("Name= {0} Surname= {1} Category= {2}", customer.Name, customer.Surname, customer.Category));
        Console.Read();

        IEnumerable<Customer> resultList3 = listOne.Except(listTwo);//**Does not work**

        foreach (var customer in resultList3)
        {
            Console.WriteLine("Name= {0} Surname= {1} Category= {2}", customer.Name, customer.Surname, customer.Category);
        }

        **//Does not work**
        var resultList2 = (listOne
                       .Where(n => !(listTwo
                           .Select(o => o.Category))
                           .Contains(n.Category)))
                       .OrderBy(n => n.Category);

        foreach (var customer in resultList2)
        {
            Console.WriteLine("Name= {0}
                             Surname= {1}
                             Category= {2}",

顾客姓名，
客户。姓氏，
客户(类别)；
}
Console.Read();

  }
}

public class Customer
{
    public string Name { get; set; }
    public string Surname { get; set; }
    public string Category { get; set; }
}

最佳答案

问题的症结在于Customer对象没有.Equals()实现。如果覆盖.Equals(and .GetHashCode)，则.Distinct将使用它来消除重复项。但是，如果您不拥有Customer实现，则不可以选择添加.Equals。

另一种方法是将custom IEqualityComparer传递给.Distinct()。这使您可以根据传入的比较器以不同的方式比较对象。

另一种选择是对重要字段进行分组，并从组中获取任何项目(因为在这种情况下，分组为.Equals)。这需要编写最少的代码。

例如

    var result = listOne.Concat(listTwo)
        .GroupBy(x=>x.Category+"|"+x.Name+"|"+x.Surname)
        .Select(x=>x.First());

得到您想要的结果。

关于linq - 合并2个列表并删除重复项。在第三个列表中输出。我的尝试不起作用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/3682437/