c# - lambda 外部子查询迭代变量评估的次数

Question

来自LINQ Quiz Q4和Q5的问答

colors 数组定义为:

string[] colors = { "green", "brown", "blue", "red" };

并从 Q4 的答案中查询:

var query =
  from c in colors
  where c.Length == colors.Max (c2 => c2.Length)
  select c;

我是否正确理解外部查询迭代表达式 c2.Length 将被计算 16 次？

也就是说，对于 colors 数组中的每个项目 с，将评估 colors.Max (c2 => c2.Length)一次，即 Max() 计算将总共进行 4 次。对于每个 Max() 评估，c2.Length 会被找到 4 次？

Answer 1

是的，没错。如果你有 LINQPad，也很容易检查:

string[] colors = { "green", "brown", "blue", "red" };

int count = 0;

var query =
    from c in colors
    where c.Length == colors.Max (c2 => 
        {
            count.Dump();
            count++;
            return c2.Length;
        }
    )
    select c;

query.Dump();