将列表复制到新列表-更加高效&最佳实践 [英] copying a list to a new list - More efficient & Best Practice

问题描述

将列表复制到新列表的适当方法是什么?将列表复制到新列表的最有效方法是什么?

What is the appropriate way of copying a list to a new list? And What is the most efficient way of copying a list to a new list?

在幕后框架的意义上，更高效，而不是代码效率.

By efficient, not code efficiency, more in the behind the scenes framework sense.

List<String>List2 = List.ToList();

或:

List<String>List2 = new List<String>();
foreach (string item in List)
{
 List2.Add(item);
}

更新:

效率更高的IL代码又如何呢?

What about more efficient IL code?

推荐答案

ToList的作用(缩短):

What ToList does (shortened):

public static List<TSource> ToList<TSource>(this IEnumerable<TSource> source)
{
    return new List<TSource>(source);
}

列表ctor的作用(简称):

What List ctor does (shortened):

public List(IEnumerable<T> collection)
{
    ICollection<T> collection2 = collection as ICollection<T>;
    int count = collection2.Count;
    this._items = new T[count];
    collection2.CopyTo(this._items, 0);
    this._size = count;
}

因此ToList()效率更高-它确实先分配空间，然后一步一步复制所有项目.

So the ToList() is much more efficient - it does allocate the space first and then copy all items in one step.

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