C＃未能里面的IEnumerable设置属性 [英] C# failing to set property inside IEnumerable

问题描述

见过怪异的行为一点在一些C＃code，我是处于亏损状态来解释。可能是我失踪的理解的重要一点，所以希望有人在那里可以在光开关的我。

Seen a weird bit of behaviour in some C# code that I'm at a loss to explain. Could be I'm missing an important bit of understanding, so hoping someone out there can switch on the light for me.

得到了code块，看起来是这样的：

Got a block of code that looks like this:

    IEnumberable<myObject> objects = GetObjectsFromApiCall();

    for (int i = 0; i < objects.Count(); i++)
        {
            if (String.IsNullOrEmpty(objects.ElementAt(i).SubObject.Title))
            {
                SubObject sub = GetSubObjectFromDatabase((long)objects.ElementAt(i).SubObject.Id);
                if (sub != null)
                {
                    objects.ElementAt(i).SubObject.Title = sub.Title;
                }
            }
        }

当你通过它一步，一切关于这code似乎正常工作。 对象集合填充预期。为收集并拥有全套预期的性能，其中包括一个人口Title属性的子是牵强。在执行过程中被抛出任何错误。

When you step through it, everything about this code seems to work properly. The "objects" collection is populated as expected. "sub" is fetched as collected and has a full set of expected properties, including a populated Title property. No errors are thrown during execution.

但是...的SubObject.Title属性（它只是有标准搞定;设置code），存在于每个对象固执地保持为空

But ... the SubObject.Title property (which just has standard get; set; code) that exists in each Object stubbornly remains empty.

我不知所措。谁能解释这是怎么回事？

I'm at a loss. Anyone explain what's going on?

编辑：对于那些谁建议我不应该用一个for循环的ElementAt，我开始与foreach循环，但认为这可能是问题的根源，因为它是获取一个新的子对象每次轮。现在固定，感谢你们的帮助，给ForEach恢复。

For those who suggested I shouldn't use a for loop and ElementAt, I started with a foreach loop but thought it might be the source of the problem because it was fetching a new SubObject each time round. Fixed now, thanks to your help, and the ForEach restored.

干杯， 马特

推荐答案

我会解决这种方式：

var objects = GetObjectsFromApiCall().ToList();

然后，你可以保持环路是（它的工作原理），或优化有点用的foreach和一些LINQ的所建议的其他答案，但它并不真正的问题：问题是，你试图改变中的一个元素一个IEnumerator＆LT;>在解释这个问题通过@AhmetKakıcı指出

Then you could keep the loop as is (it works), or optimize it a bit using foreach and some Linq as suggested by other answers, but it does not really matter: the problem was that you attempted to change an element on an IEnumerator<> as explained in this question pointed by @Ahmet Kakıcı.

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