C#对另一个列表元素的引用列表 [英] C# List of references to another list elements

问题描述

我想用对注释列表元素的引用来构建一个子列表(我只需要少数几个满足条件的元素).

I want to build a sublist with references to the elements of anoter list (i need few of them, that are meeting the conditions).

我该怎么做:

        List<int> mainList = new List<int>();
        List<int> subList = new List<int>();
        mainList.Add(5);
        subList.Add(mainList[0]); //case 1
        //subList[0] = mainList[0]; //case 2
        Console.WriteLine("{0}", mainList[0]);
        Console.WriteLine("{0}", subList[0]);
        subList[0]++;
        Console.WriteLine("{0}", mainList[0]);
        Console.WriteLine("{0}", subList[0]);
        mainList[0]+=2;
        Console.WriteLine("{0}", mainList[0]);
        Console.WriteLine("{0}", subList[0]);

在第一种情况下，我得到的是副本而不是引用，因为控制台输出是:

In the first case i'm getting the copy instead of reference because the console output is:

5
5
5
6
7
6

在第二种情况下，我收到 ArgumentOutOfRangeException 因为 subList[0] 未初始化.那么，我该怎么办呢?

In the second case i'm getting ArgumentOutOfRangeException because subList[0] is not initialized. So, how can i do this?

另外，根据速度/内存使用情况，最好保留mainList的inedexe的 List< int> 而不是引用吗?

Also, according to speed/memory usage may be it's even better to keep List<int> of inedexes of the mainList instead of references?

推荐答案

由于@ManIkWeet和@Florian，我找到了解决方案:

Thanks to @ManIkWeet and @Florian, i've found the solution:

        public class TestClass{
           public int value;
        }

        ...

        List<TestClass> mainList = new List<TestClass>();
        List<TestClass> subList = new List<TestClass>();
        mainList.Add(new TestClass { value = 5 });
        subList.Add(mainList[0]);
        Console.WriteLine("{0}", mainList[0].value);
        Console.WriteLine("{0}", subList[0].value);
        subList[0].value++;
        Console.WriteLine("{0}", mainList[0].value);
        Console.WriteLine("{0}", subList[0].value);
        mainList[0].value+=2;
        Console.WriteLine("{0}", mainList[0].value);
        Console.WriteLine("{0}", subList[0].value);

输出为:

5
5
6
6
8
8

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