如何使用 linq 从 List 中删除两个属性的重复组合的对象？

Question

与this one 相同的问题，但我需要从 List 中删除具有两个属性的重复组合的对象。

有一组对象，对象有年龄和名称：

21 Carl
23 Vladimir
25 Bob
21 Olivia
21 Carl
30 Jacob
23 Vladimir

输出列表应包含：

21 Carl
23 Vladimir
25 Bob
21 Olivia
30 Jacob

如何删除它？

Answer 1

试试这个：

  public class KeyValueClass
    {
        public int Age { get; set; }
        public string Name { get; set; }
    }

    private void DoTheJob()
    {

        var myList = new List<KeyValueClass>
        {
            new KeyValueClass {Age = 21, Name = "Carl"},
            new KeyValueClass {Age = 23, Name = "Vladimir"},
            new KeyValueClass {Age = 25, Name = "Bob"},
            new KeyValueClass {Age = 21, Name = "Olivia"},
            new KeyValueClass {Age = 21, Name = "Carl"},
            new KeyValueClass {Age = 30, Name = "Jacob"},
            new KeyValueClass {Age = 23, Name = "Vladimir"},
        };

        var myDistinctList = myList.GroupBy(x => new { x.Age, x.Name })
            .Select(c => c.First()).ToList();
    }

Answer 2

只需使用 ISet 即可避免 List 的开销和性能下降：

public class Person : IEquatable<Person> 
{
    public int Age { get; private set;}
    public string Name { get; private set;}

    public bool override Equals(Person other){
        return other.Age == Age && other.Name.Equals(Name);
    }

    public override int GetHashCode(){
        return Age.GetHashCode() ^ Name.GetHashCode();
    }
}

private IEnumerable<Person> MakeUniqueList(IEnumerable<Person> input){
    return new HashSet<Person>(input);
}

为了真正删除，这会降低性能（但会节省内存使用），请使用 List.Remove(T) https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1.remove?view=netframework-4.7.2

Answer 3

您可以使用 Linq 命名空间中的 Distinct() 和 IEqualityComparer：

class Program
{
    static void Main(string[] args)
    {


        List<KeyValueClass> myList = new List<KeyValueClass>
            {
                new KeyValueClass {Age = 21, Name = "Carl"},
                new KeyValueClass {Age = 23, Name = "Vladimir"},
                new KeyValueClass {Age = 25, Name = "Bob"},
                new KeyValueClass {Age = 21, Name = "Olivia"},
                new KeyValueClass {Age = 21, Name = "Carl"},
                new KeyValueClass {Age = 30, Name = "Jacob"},
                new KeyValueClass {Age = 23, Name = "Vladimir"},
            };

        var myDistincList = myList.Distinct(new KeyValueEqualityComparer());

        foreach (var item in myDistincList) { Console.WriteLine("Age: {0}, Name:{1}", item.Age, item.Name); }

        Console.ReadKey();
    }
}


public class KeyValueClass 
{
    public int Age { get; set; }
    public string Name { get; set; }
}



class KeyValueEqualityComparer : IEqualityComparer<KeyValueClass>
{
    public bool Equals(KeyValueClass x, KeyValueClass y)
    {
        if (x == null || y == null) return false;
        if (x.Age == y.Age && x.Name.Equals(y.Name)) return true;
        return false;
    }

    public int GetHashCode(KeyValueClass obj)
    {
        return (obj.Age + obj.Name).GetHashCode() + 387;
    }
}