将对象强制转换为IEnumerable< object&gt ;?

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如何将对象转换为 IEnumerable< object> ？

我知道对象实现 IEnumerable< object> 但我不知道它是什么类型。它可以是数组， List 或任何。

一个简单的测试用例我试图工作：

static void Main（string [] args） { object arr = new [] {1，2，3，4，5}; foreach（var item in arr as IEnumerable< object>） Console.WriteLine（item）; Console.ReadLine（）; }

解决方案

一个具体的用例，但你可以发现它足以简单地转换到非通用的 IEnumerable 接口。

有两个原因为什么这通常适用于被认为是序列的大多数类型。

经典.NET 1.x集合类实现 IEnumerable 。

通用 IEnumerable< T> 接口从 IEnumerable 继承，所以cast应该适用于System.Collections.Generic中的通用集合类，

：

至于为什么你提供的示例不工作：

这不会在C＃3，因为它不支持通用接口协方差 - 您不能将 IEnumerable< Derived> 视为 IEnumerable< Base> 。

即使 IEnumerable< T> 是协变的，因为值类型不支持方差，这在C＃从 int [] （ IEnumerable< int> ） IEnumerable< object> 无法成功。

How can I cast an object to IEnumerable<object>?

I know that the object implements IEnumerable<object> but I don't know what type it is. It could be an array, a List<T>, or whatever.

A simple test case I'm trying to get working:

static void Main(string[] args) { object arr = new[] { 1, 2, 3, 4, 5 }; foreach (var item in arr as IEnumerable<object>) Console.WriteLine(item); Console.ReadLine(); }

解决方案

It's hard to answer this without a concrete use-case, but you may find it sufficient to simply cast to the non-generic IEnumerable interface.

There are two reasons why this will normally work for most types that are considered "sequences".

The "classic" .NET 1.x collection classes implement IEnumerable.

The generic IEnumerable<T> interface inherits from IEnumerable, so the cast should work fine for the generic collection classes in System.Collections.Generic, LINQ sequences etc.

EDIT:

As for why your provided sample doesn't work:

This wouldn't work in C# 3 because it doesn't support generic interface covariance - you can't view an IEnumerable<Derived> as an IEnumerable<Base>.

This wouldn't work in C# 4 either despite the fact that IEnumerable<T> is covariant, since variance is not supported for value-types - the cast from int[] (an IEnumerable<int>) --> IEnumerable<object> can't succeed.