如何获得扩展方法来更改原始对象? [英] How can I get an extension method to change the original object?

问题描述

我希望能够编写扩展方法，以便我可以说:

I want to be able to write extension methods so that I can say:

lines.ForceSpaceGroupsToBeTabs();

代替:

lines = lines.ForceSpaceGroupsToBeTabs();

但是，以下代码当前输出:

However, the following code currently outputs:

....one
........two

代替:

Tone
TTtwo

我必须在以下代码中更改什么才能使其输出:

Tone
TTtwo

(注意，对于可见性，.= space, T = ):

(note that for visibility, . = space, T = ):

using System;
using System.Collections.Generic;

namespace TestExtended82343
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> lines = new List<string>();
            lines.Add("....one");
            lines.Add("........two");

            lines.ForceSpaceGroupsToBeTabs();

            lines.ForEach(l => Console.WriteLine(l));
            Console.ReadLine();
        }
    }

    public static class Helpers
    {
        public static void ForceSpaceGroupsToBeTabs(this List<string> originalLines)
        {
            string spaceGroup = new String('.', 4);
            List<string> lines = new List<string>();
            foreach (var originalLine in originalLines)
            {
                lines.Add(originalLine.Replace(spaceGroup, "T"));
            }
            originalLines = lines;
        }
    }
}

推荐答案

你必须修改传递给扩展方法的 List 的内容，而不是保存引用的变量名单:

You have to modify the contents of the List<string> passed to the extension method, not the variable that holds the reference to the list:

public static void ForceSpaceGroupsToBeTabs(this List<string> lines)
{
    string spaceGroup = new String('.', 4);
    for (int i = 0; i < lines.Count; i++)
    {
        lines[i] = lines[i].Replace(spaceGroup, "T");
    }
}

这篇关于如何获得扩展方法来更改原始对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！