我如何重写的ToString（），并实现通用？ [英] How do I override ToString() and implement generic?

问题描述

我有我想要做如下修改code：

I have code that I want to make the following changes:

1. 我如何重写的ToString（）？它说：静态成员...的ToString（System.Collections.Generic.List）'不能被标记为覆盖，虚拟或抽象的

1. How do I override ToString()? It says: A static member ...ToString(System.Collections.Generic.List)' cannot be marked as override, virtual, or abstract.

我如何使它通用？

public static override string ToString(this List<int> list) {
    string output = "";
    list.ForEach(item => output += item.ToString() + "," );
    return output;
}

谢谢！

推荐答案

什么是你想达到什么目的？我常常想输出列表的内容，所以我创建了以下扩展方法：

What are you trying to achieve? Often I want to output the contents of a list, so I created the following extension method:

public static string Join(this IEnumerable<string> strings, string seperator)
{
    return string.Join(seperator, strings.ToArray());
}

然后将其消耗掉这样

It is then consumed like this

var output = list.Select(a.ToString()).Join(",");

修改：为了更方便使用非字符串列表，这里是上述

EDIT: To make it easier to use for non string lists, here is another variation of above

public static String Join<T>(this IEnumerable<T> enumerable, string seperator)
{
    var nullRepresentation = "";
    var enumerableAsStrings = enumerable.Select(a => a == null ? nullRepresentation : a.ToString()).ToArray();
    return string.Join(seperator, enumerableAsStrings);
}

public static String Join<T>(this IEnumerable<T> enumerable)
{
    return enumerable.Join(",");
}

现在你可以使用它像这样

Now you can consume it like this

int[] list = {1,2,3,4};
Console.WriteLine(list.Join()); // 1,2,3,4
Console.WriteLine(list.Join(", ")); // 1, 2, 3, 4
Console.WriteLine(list.Select(a=>a+".0").Join()); // 1.0, 2.0, 3.0, 4.0

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