列表中的列表不打印元素，而是显示 System.Collections.Generic.List`1[System.Object] [英] List inside list does not print elements, instead shows System.Collections.Generic.List`1[System.Object]

问题描述

我有一个包含三个项目的列表.第一个元素是整数，第二个也是整数，第三个是另一个列表.通过使用 for 每个循环，我可以打印这些项目.

I have a list which contains three items. First element is integer, second one is also an integer and third one is another list. By using for each loop I'm able to print these items.

List<object> mainList= new List<object>();

mainList.Add(binRead.ReadInt32()); // Reads first integer ant adds to mainList
mainList.Add(binRead.ReadInt32()); // Reads second integer ant adds to mainList

List<object> avlDataList = new List<object>();

for(int i=0; i<n; i++)
{
  // Reads some data and adds it to avlDataList
}

mainList.Add(avlDataList); // Adds that list to mainList

foreach(var i in mainList)
{
   Console.WriteLine(i); // Prints items      
}

我得到这个输出:

8
1
System.Collections.Generic.List`1[System.Object]

如何修改我的代码以查看该列表中的内容而不是收到此消息?avlDataList 列表有 10 个元素.所以我想总共看到 12 个元素.

How can I modify my code to see what's inside of that list instead of getting this message? That avlDataList list has 10 elements. So i would like to see 12 elements in total.

推荐答案

根据 MKasprzyk 的回答，您可以在遍历主列表时检查每个对象的类型，以决定如何将其输出到控制台.否则将调用默认的 ToString() 方法(见下文).

As per MKasprzyk's answer, you can check the type of each object when iterating through the main list to decide how to output it to the console. Otherwise the default ToString() method will be called (see below).

如果您使用的是 C# 7，您可以(可以说)通过使用 switch 模式匹配来提高可读性，只需编写:

If you are using C# 7, you can (arguably) increase readability by using switch pattern matching and simply write:

foreach (var i in mainList)
{
    switch (i)
    {
        case IEnumerable<object> li:
            Console.WriteLine($"List: {string.Join(", ", li)}");
            break;
        default:
            Console.WriteLine(i);
            break;
    }
}

这种方式，目前输出的是不可枚举的对象，而输出实现了IEnumerable