在抽象类中使用泛型 [英] Using generics in abstract classes

问题描述

我正在开发一个抽象类，其中实现类需要实现 T 的列表.问题是这不起作用:

I'm working on an abstract class where the implementing class needs to implement a list of T. The problem is that this doesn't work:

public class AbstractClass
{
    public int Id { get; set; }
    public int Name { get; set; }

    public abstract List<T> Items { get; set; }
}

public class Container : AbstractClass
{
    public List<Widgets> Items { get; set; }
}

我确定我缺少一个明显的答案，并且我知道我可以构建一个抽象基类型以放入列表，但是当我使用 Linq 命令构建列表时，抽象type (ItemBase) 不能很好地与 .ToList() 方法配合使用.我正在尝试做的事情很独特吗?

I'm sure that there is an obvious answer that I'm missing, and I know that I can build an abstract base type to put in the list, but when I use my Linq command to build the list, the abstract type (ItemBase) doesn't play nicely with the .ToList() method. Is what I'm trying to do so unique?

推荐答案

你还需要类上的声明，才能知道 T 是什么类型:

You need the declaration on the class as well, to know what type T is:

public abstract class AbstractClass<T>
{
    public int Id { get; set; }
    public int Name { get; set; }

    public abstract List<T> Items { get; set; }
}

public class Container : AbstractClass<Widgets>
{
    public override List<Widgets> Items { get; set; }
}

你也可以限制 T 可以是什么，比如说它必须实现 IWidgets:

You can also restrict what T can be, like say it must implement IWidgets:

public class AbstractClass<T> where T : IWidgets

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