c# - 需要有关 Enumerable.Aggregate 函数的更多详细信息

Question

你能帮我理解吗，

       words.Aggregate((workingSentence, next) => + next + " " + workingSentence);   

从下面的代码片段？如果有人向我解释如何在 C# 1.1 中实现这一点，那就太好了。

(来自 MS 的片段)-

        string sentence = "the quick brown fox jumps over the lazy dog";
        // Split the string into individual words.
        string[] words = sentence.Split(' ');
        // Prepend each word to the beginning of the 
        // new sentence to reverse the word order.
        string reversed = words.Aggregate((workingSentence, next) =>
                                              next + " " + workingSentence);
        Console.WriteLine(reversed);
        // This code produces the following output:
        //
        // dog lazy the over jumps fox brown quick the

Answer 1

您的示例的 Aggregate 部分转换为大致如下的内容:

string workingSentence = null;
bool firstElement = true;
foreach (string next in words)
{
    if (firstElement)
    {
        workingSentence = next;
        firstElement = false;
    }
    else
    {
        workingSentence = next + " " + workingSentence;
    }
}
string reversed = workingSentence;

workingSentence 变量是一个累加器，它通过对现有累加器值和序列的当前元素应用一个函数，在循环的每次迭代中更新；这是由您的示例中的 lambda 执行的，在我的示例中由 foreach 循环的主体执行。