铸造通用类型的对象亚型 [英] Casting generic typed object to subtype

问题描述

我有以下情形在我的代码：

I have the following scenario in my code:

class Document
{}

class Track : Document
{}

class ViewListClickHandler
{
    // I can't change that signature, it's provided by a library I use.
    protected override void click(object theList, int index)
    {
        // I here need to cast "theList" to IList<T> where T : Document
    }
}

我现在的问题是（书面在注释）：

My question now is (as written at the comment):

我怎样才能施放该的thelist 一类像的IList< ; T>其中T：文档

How can I cast that theList to a type like IList<T> where T : Document?

在这种情况下，困难的是，我可以得到任何类，延长文件在该列表中。而且它是相同的，我是我所得到。我只是想将它转换为包含若干文件清单

The difficulty in this case is, that I can get any class, extending Document in that list. And it's the same for me what I get. I just want to cast it to a list containing some documents.

编辑：

对不起，忘了提，。 的thelist 有时是一个对象，以 LT兼容的IList&;文件> ，有时的IList<轨道> 或一般类型为文件的其他一些亚型。

Sorry, forgot to mention that. theList sometimes is an object, compatible to IList<Document>, sometimes IList<Track> or generically typed to some other subtype of Document.

我需要做的在一衬垫。我有一个例子，它是不是一个IList，但另一个一般类型类，在这里我不能循环。

I need to do that in a one-liner. I have another example, where it isn't an IList, but another generically typed class, where I can't loop.

推荐答案

您可以使用 OfType

var documents = theList.OfType<Document>();

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