函数返回一个泛型类型，其值只在运行时已知 [英] Function returning a generic type whose value is known only at runtime

问题描述

我需要使用像下面这样的通用接口：

I need to use a generic interface like the following:

public interface IContainer<T>
{
    IEnumerable<IContent<T>> Contents { get; }
}

实现此接口的对象由类似以下的通用方法返回：

An object implementing this interface is returned by a generic method like the following:

IContainer<T> GetContainer<T>(IProperty property);

键入 T 是未知的，直到运行时

Type T is unknown until run-time.

使用反射，我能够调用 GetContainer< T> 方法得到的结果。

Using reflection I am able to invoke the GetContainer<T> method and get the result.

我的问题是，我不知道如何枚举其类型为对象（所以我不能结果它转换为的IEnumerable ）。

My problem is that I don't know how to enumerate the result which has type Object (therefore I cannot cast it to IEnumerable).

我也试着铸造如下，但它不工作（它说类型预计）：

I have also tried casting as follows but it does not work (it says "Type is expected"):

var myContainer = genericMethodInfo.Invoke(
                           myService, 
                           new object[] { property })
    as typeof(IContainer<>).MakeGenericType(type);

其中，键入是运行时类型，为myService 是服务暴露 GetContainer< T> 方法，以及属性的类型的iProperty 的需要。

where type is the runtime type, myService is the service exposing the GetContainer<T> method, and property is of type IProperty as needed.

更新：看到我的完整的解决方案在我的博客：的 http://stefanoricciardi.com/2010/02/18/generics-with-type-uknown-at-compile-time/

UPDATE: see my complete solution in my blog: http://stefanoricciardi.com/2010/02/18/generics-with-type-uknown-at-compile-time/

推荐答案

typeof运算（的IContainer<>）MakeGenericType（类型）将只在运行时进行评估，而为。 。需要知道在编译时的类型

typeof(IContainer<>).MakeGenericType(type) will only evaluate at runtime, while "as" needs to know the type at compiler time.

我真不明白，是这条评论：我的问题是，我不知道如何枚举其结果具有Object类型（所以我不能将它转换为IEnumerable的）。

What I really don't understand is this comment: My problem is that I don't know how to enumerate the result which has type Object (therefore I cannot cast it to IEnumerable).

myContainer中可能是一个对象，但它一定能够转换为IEnumerable的？如果它不能那么它不能枚举

myContainer may be an Object but it can surely be cast to IEnumerable? If it can't then it can't be enumerated.

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