在列表中逐项添加项目的快捷方式? [英] Short way to add item after item in List?

问题描述

除了foreach循环和新集合创建之外，是否还有其他方法可以在现有List中的特定对象之后添加对象?

If there any short way besides foreach loop and new collection creation to add object after specific object in existing List ?

只是一个例子:

"amy"，"jerry"，"tony"，"amy"，"jack".我想以简短的方式在每个"amy"之后添加"simon"

"amy","jerry","tony","amy","jack". I want to add "simon" after each "amy" in short way

推荐答案

您可以使用Linq来做到这一点.

You can use Linq to do this.

foreach (var item in values
          .Select((o, i) => new { Value = o, Index = i })
          .Where(p => p.Value == "amy")
          .OrderByDescending(p => p.Index))
{
    if (item.Index + 1 == values.Count) values.Add("simon");
    else values.Insert(item.Index + 1, "simon");
} 

使用foreach，但您可以将其放入扩展方法中以保持代码清晰.

Uses a foreach but you can put it into a extension method to keep the code clear.

您可以轻松地将其放入扩展方法中.

You can easily put this into a extension method.

public static void AddAfterEach<T>(this List<T> list, Func<T, Boolean> condition, T objectToAdd) 
{
    foreach (var item in list.Select((o, i) => new { Value = o, Index = i }).Where(p => condition(p.Value)).OrderByDescending(p => p.Index))
    {
        if (item.Index + 1 == list.Count) list.Add(objectToAdd);
        else list.Insert(item.Index + 1, objectToAdd);
    } 
}

现在通话:

List<String> list = new List<String>() { "amy","jerry","tony","amy","jack" };
list.AddAfterEach(p => p == "amy", "simon");

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