为什么在向列表中添加其他对象时，此ploymorphic List属性为null？ [英] Why does this ploymorphic List property go null when adding additional objects to the list?

问题描述

请考虑以下内容：

public class VideoContainer<T>
{
    public string Name { get; set; }
    //public List<VideoContainer<T>> VideoContainers { get; set; }
}

public class Perspective : VideoContainer<Perspective>
{
    public List<VideoContainer<SourceContainer>> VideoContainers { get; set; }
}

我想确保 VideoContainer< Perspective> ;. VideoContainers 只能包含 VideoContainer< SourceContainer> 类型。

I want to ensure VideoContainer<Perspective>.VideoContainers can only contain VideoContainer<SourceContainer> types.

我向列表<透视图> 添加一个新的 Perspective $ c>与三个 VideoContainers 。问题是，当我向列表中添加一个新的Perspective时，之前添加的 Perspective.VideoContainers 为null。

I add a new Perspective object to a List<Perspective> with three VideoContainers. The problem is that when I add a new Perspective to the list, the previously-added Perspective.VideoContainers is null.

为什么会发生这种情况？

Why is this happening?

推荐答案

听起来你需要两个通用类型：

It sounds like you need two generic types:

public class VideoContainer<T, U>
{
    public string Name { get; set; }
    public List<VideoContainer<U>> VideoContainers { get; set; }
}

public class Perspective : VideoContainer<Perspective, SourceContainer>
{
    // No longer declare the list, just use it... it's now:
    // public List<VideoContainer<SourceContainer>> VideoContainers { get; set; }
}

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