在迭代器中访问C＃基类会导致ReSharper警告 [英] accessing C# base class in iterator causes ReSharper warning

问题描述

我有两个类， GenericList 和 SpecificList ，其中 SpecificList 继承自 GenericList 。 GenericList 实现 IEnumerable< GenericItem> 和 SpecificList 实现的IEnumerable< SpecificItem> 。 SpecificItem 继承自 GenericItem 。我必须在 GenericList 和 SpecificList 中实现 GetEnumerator 他们实现 IEnumerable< T> 。在 GenericList 中，这很简单，我只返回基础列表< T> 的枚举器：

I have two classes, GenericList and SpecificList, where SpecificList inherits from GenericList. GenericList implements IEnumerable<GenericItem> and SpecificList implements IEnumerable<SpecificItem>. SpecificItem inherits from GenericItem. I have to implement GetEnumerator in both GenericList and SpecificList since they implement IEnumerable<T>. In GenericList, it's easy enough, I just return the enumerator for the underlying List<T>:

public IEnumerator<GenericItem> GetEnumerator()
{
    return genericItemsList.GetEnumerator();
}

但是，在$ code> SpecificList ，看起来比较棘手。将 IEnumerator< GenericItem> 转换为 IEnumerator< SpecificItem> 似乎有风险，我不知道是否会甚至工作。相反，我做了以下事情：

However, in SpecificList, it seems trickier. It seems risky to cast IEnumerator<GenericItem> to IEnumerator<SpecificItem>, and I don't know if that would even work. Instead, I did the following:

public new IEnumerator<SpecificItem> GetEnumerator()
{
    IEnumerator<GenericItem> enumerator = base.GetEnumerator();
    while (enumerator.MoveNext())
    {
        yield return (SpecificItem)enumerator.Current;
    }
}

这个编译很好，一个简单的MSTest单元测试调用 SpecificList.GetEnumerator（）似乎表明它有效。但是，ReSharper在上述方法中突出显示 base ，并显示以下警告：

This compiles fine and a simple MSTest unit test calling SpecificList.GetEnumerator() seems to show it works. However, ReSharper highlights base in the above method with the following warning:

Access从匿名方法，lambda表达式，查询表达式或迭代器通过'base'关键字到GenericList.GetEnumerator导致无法验证的代码

Access to GenericList.GetEnumerator through 'base' keyword from anonymous method, lambda expression, query expression or iterator results in unverifiable code

这是什么东西我应该担心吗？我应该采用不同的方式吗？

Is this something I should worry about? Should I do something differently?

编辑：我正在使用ReSharper 5.1完整版预发布版本5.1.1715.35。

I'm using ReSharper 5.1 Full Edition Pre-Release Build 5.1.1715.35.

另外，我应该暂停运行MSTest单元测试：我只需按 Ctrl + R ， Ctrl < Chrome中的/ kbd> + T 重新加载页面...

Also, I should take a break from running MSTest unit tests: I just hit Ctrl+R, Ctrl+T in Chrome to reload the page...

推荐答案

R＃是正确的在3.0版本的C＃编译器中访问迭代器/ lambda中的 base 关键字可能会导致无法验证的代码。当它有或没有时有点复杂，我不会试图在这里覆盖它。

R# is correct that accessing the base keyword inside an iterator / lambda in the 3.0 version of the C# compiler could result in unverifiable code. When it does or doesn't is a bit complex and I won't attempt to cover it here.

解决此问题的最简单方法是将调用包装到另一个非静态私有的 base.GetEnumerator 中来自迭代器的方法和引用。

The easiest way to work around this is to wrap the call to base.GetEnumerator in another non-static private method and reference that from your iterator.

private IEnumerator<GenericItem> GetBaseEnumerator() {
  return base.GetEnumerator();
}

public new IEnumerator<SpecificItem> GetEnumerator()
{
    IEnumerator<GenericItem> enumerator = GetBaseEnumerator();
    while (enumerator.MoveNext())
    {
        yield return (SpecificItem)enumerator.Current;
    }
}

我很确定这个错误已在4.0版本的C＃编译器。

I'm fairly certain this bug was fixed in the 4.0 version of the C# compiler.

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