的foreach变化没有被保存LINQ的项目集合 [英] Foreach changes not being preserved on Linq item collection

问题描述

在下面的例子中，在foreach应用的更改，当我返回集合将不会保留：

In the following example, changes applied in the foreach are not preserved when I return the collection:

var people = SomeLinqToSqlSource();

foreach (var person in people)
{
   person.Name = "Jimmy";
}

return people.AsQueryable();

这违背我的理解是一个foreach（..）内，您可以通过引用在当前操作项目。

This contradicts my understanding that within a foreach(..), you operate by-reference on the current item.

有谁请让我知道我要去哪里错了？

Could anybody please let me know where I'm going wrong?

感谢。

推荐答案

的问题是，人是 IQueryable的并重新查询，当您返回它和消费者列举的结果 - 现在你更新的属性都消失了，因为每个人实例是通过执行重建查询。

The problem is that people is an IQueryable and is re-queried when you return it and the consumer enumerates the results - your updated properties are gone now, since each person instance is reconstructed by executing the query.

如果您想保留你必须先兑现你的数据，即采用了ToList（）修改然后返回列表作为的IEnumerable （或的IList ）

If you want to preserve changes you have to materialize your data first, i.e. using ToList() and then return the list as an IEnumerable (or IList)

这篇关于的foreach变化没有被保存LINQ的项目集合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！