根据其属性删除列表中的重复对象 [英] removing duplicate objects in a list based on its properties

问题描述

如何从列表中删除重复的对象?
例如:

列表(MyObject)列表= 新列表

myObject.SomeAttribute = x; 

我想通过查看每个对象的属性来删除重复项.

可以使用一个有效的代码示例

解决方案

请参见以下代码:

 使用系统；
使用 System.Collections.Generic;
使用 System.Text；
使用 System.Linq;

命名空间 t1
{
    类 MyClass
    {
        公共  int ?属性{获取； 集;}
        公共  int  ID { get ; 集;}
    }

    类 MyClassComparer:IEqualityComparer< MyClass>
    {
        公共 布尔等于(MyClass x，MyClass y)
        {
            如果(对象 .ReferenceEquals(x，y))返回  true ;
            如果(对象.ReferenceEquals(x，空)|| 对象 .ReferenceEquals(y，空))
                返回 假；
            返回 x.property == y.property;
        }

        公共  int  GetHashCode(MyClass myObject)
        {
            如果(对象.ReferenceEquals(myObject，空))返回  0 ;

             int  hashObjectProperty = myObject.property == 空?  0 :myObject.property.GetHashCode();

            返回 hashObjectProperty;
    }
    }

     class 程序
    {
        静态 无效 Main()
        {
            列表< MyClass> list = 新 List< MyClass>();

            Console.WriteLine(" );

             foreach ( int 在 in 中可枚举.范围( 1 ， 10 ))
            {
                list.Add(新 MyClass {ID = i，property =(i&  1 )}));
                Console.WriteLine(" ，i，i和 1 )；
            }

            Console.WriteLine(" )；

             foreach (在  列表中的MyClass myObject  keyword>新 MyClassComparer()) )
            {
                Console.WriteLine(" ，myObject.ID，myObject.财产);
            }

            Console.ReadKey();
        }

    }
} 

如您所见，如果运行它，IEnumerble.Distinct将在适当的比较器的帮助下为您完成这项工作，但是它将保留第一次出现的情况.因此，正如我在评论中提到的那样，您需要通过实现适当的 IEqualityComparer ^ ]-这也可以帮助您:用于Linq Distinct()的通用IEqualityComparer [ ^ ]

How do I remove duplicate objects from a list?
For example:

List(MyObject) list = new list

myObject.SomeAttribute = x;

I want to remove the duplicates by looking at each object''s attribute.

A working code example would be appreciated

解决方案

See following code:

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

namespace t1
{
    class MyClass
    {
        public int? property {get; set;}
        public int ID {get; set;}
    }

    class MyClassComparer : IEqualityComparer<MyClass>
    {
        public bool Equals(MyClass x, MyClass y)
        {
            if (Object.ReferenceEquals(x, y)) return true;
            if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
                return false;
            return x.property == y.property;
        }

        public int GetHashCode(MyClass myObject)
        {
            if (Object.ReferenceEquals(myObject, null)) return 0;

            int hashObjectProperty = myObject.property == null ? 0 : myObject.property.GetHashCode();

            return hashObjectProperty;
    }
    }

    class Program
    {
        static void Main()
        {
            List<MyClass> list = new List<MyClass>();

            Console.WriteLine("\nOriginal list:");

            foreach(int i in Enumerable.Range(1,10))
            {
                list.Add(new MyClass{ ID = i, property = (i & 1)});
                Console.WriteLine("{0} => {1}", i, i & 1);
            }

            Console.WriteLine("\nDistinct by property:");

            foreach(MyClass myObject in list.Distinct(new MyClassComparer()))
            {
                Console.WriteLine("{0} => {1}", myObject.ID, myObject.property);
            }

            Console.ReadKey();
        }

    }
}

As you will see if you run it, IEnumerble.Distinct will do the job for you with the help of a proper comparer, but it will leave the first occurrences. Thus, as I mentioned in my comment, you need to define the comparison means by implementing a proper IEqualityComparer[^] - this one could also help you: A Generic IEqualityComparer for Linq Distinct()[^]

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