如何使用 linq 从 List 中删除两个属性的重复组合的对象？

Question

与这个问题相同的问题，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age和Name：21 Carl23 Vladimir25 Bob21 Olivia21 Carl30 Jacob23 Vladimir输出列表应包含：21 Carl23 Vladimir25 Bob21 Olivia30 Jacob如何删除它？

Answer 1

尝试这个：

  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

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;

    }

}

Answer 3

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);

}

为了实际删除，这将是相当缓慢的性能明智（但它会节省内存使用），使用 List.Remove(T) https://docs.microsoft.com/en-us/dotnet/api/system。 collections.generic.list-1.remove?view=netframework-4.7.2