检查Type或实例是否实现IEnumerable，而与Type T无关 [英] Checking if Type or instance implements IEnumerable regardless of Type T

问题描述

我在当前项目中进行了大量反思，并且尝试提供一些辅助方法以使所有内容保持整洁。

I'm doing a heavy bit of reflection in my current project, and I'm trying to provide a few helper methods just to keep everything tidy.

我希望提供一对方法来确定类型或实例是否实现 IEnumerable –不管类型是 T 。这是我目前的状态：

I'd like to provide a pair of methods to determine if a type or instance implements IEnumerable – regardless of the type T. Here is what I have at the moment:

public static bool IsEnumerable(this Type type)
{
    return (type is IEnumerable);
}

public static bool IsEnumerable(this object obj)
{
    return (obj as IEnumerable != null);
}

当我使用

Debug.WriteLine("Type IEnumerable:   " + typeof(IEnumerable).IsEnumerable());
Debug.WriteLine("Type IEnumerable<>: " + typeof(IEnumerable<string>).IsEnumerable());
Debug.WriteLine("Type List:          " + typeof(List<string>).IsEnumerable());
Debug.WriteLine("Type string:        " + typeof(string).IsEnumerable());
Debug.WriteLine("Type DateTime:      " + typeof(DateTime).IsEnumerable());
Debug.WriteLine("Instance List:      " + new List<string>().IsEnumerable());
Debug.WriteLine("Instance string:    " + "".IsEnumerable());
Debug.WriteLine("Instance DateTime:  " + new DateTime().IsEnumerable());

我得到的结果是：

Type IEnumerable:   False
Type IEnumerable<>: False
Type List:          False
Type string:        False
Type DateTime:      False
Instance List:      True
Instance string:    True
Instance DateTime:  False

类型方法似乎根本不起作用–我曾期望直接 System.Collections.IEnumerable true $ c>至少匹配。

The type method doesn't appear to work at all – I had expected a true for the direct System.Collections.IEnumerable match at least.

我知道 string 在技术上是可以枚举的，尽管有一些注意事项。但是，在这种情况下，理想情况下，我需要helper方法为其返回 false 。我只需要具有定义的 IEnumerable< T> 类型的实例即可返回 true 。

I'm aware that string is technically enumerable, albeit with a few caveats. Ideally in this case, however, I'd need the helper method to return false for it. I just need the instances with a defined IEnumerable<T> type to return true.

我可能只是错过了一些显而易见的东西–有人能指出我正确的方向吗？

I've probably just missed something fairly obvious – can anyone point me in the right direction?

推荐答案

以下行

return (type is IEnumerable);

询问是否的实例 ，类型是 IEnumerable ，显然不是。

is asking "if an instance of Type, type is IEnumerable", which clearly it is not.

您要执行的操作是：

return typeof(IEnumerable).IsAssignableFrom(type);

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