How does .net determine the order for the “foreach” loop?

Question

当我在C＃.net中使用foreach语句时，.net如何确定以什么顺序处理集合中的元素？

Answer 1

When you use foreach , the object which implements IEnumerable or IEnumerable<T> is "iterated". The order is determined by the object's implementation of IEnumerable .

Any class can customize the order in which this occurs. With a List<T> , for example, it's in the list's order (by index). However, some classes such as Dictionary<T,U> do not guarantee an order at all - only that each item will get enumerated through one time, as providing an ordering guarantee in that case would dramatically hamper performance.

Answer 2

It's using the IEnumerable and IEnumerator interfaces. They a providing the values one after another, so .Net does not have to care about ordering. It's processing the values just in the order as they are delivered.