c# – 条件类型约束参数

我有一个类,Container< T>,它有一个ContainerContents< T>. Container实际上采用两个类型约束参数Container< TContainer,TContents> – TContainer是容器的类型,TContents是它接受的内容类型.

我想确保如果TContainer是X或从X派生,那么TContents也将是X或从X派生,但是TContents不必等于TContainer.

我想表达以下几类.

>可以随身携带的东西(赃物),就像铅笔一样.
>无法携带的东西(BaSEObject),就像一棵树.
>可以容纳其他东西的东西(容器)
>无法携带的集装箱,如银行金库.
> Carriable Containers(像背包).

如果可以携带集装箱,那么其内容也必须是可携带的.但是,仅仅因为Container是一个背包并不意味着它只能携带背包.

我希望能够编码：

> var ringWorld = new Container< BigRing,CivicWork>();
> var pickleKnox = new Container< BankVault,Pickle>();
> var swagBag = new Container< ToteBag,Swag>();
> var tomeBag = new Container< ToteBag,Book>();

但不是var treeBag = new Container< Bag,Tree>();

这是我的骨架设置.

public abstract class BaSEObject
{
    private readonly string _name;

    protected BaSEObject(string name)
    {
        _name = name;
    }

    public string Name { get { return _name; } }
}

public class Swag : BaSEObject
{
    private readonly int _weight;

    public Swag(string name,int weight):base(name)
    {
        _weight = weight;
    }

    public int Weight { get { return _weight; } }
}

/* I like the flexibility of i.e.: Container<BankVault,Pickles> 
but if the container itself is carriable (Swag),then its contents 
are by nature also carriable. */

public class Container<TContainer,TContents> : BaSEObject 
    where TContainer:BaSEObject 
    where TContents:BaSEObject,or Swag if TContainer:(Swag or derived from Swag)
{
    ContainerContents<TContents> _contents;

    public Container(string name,int maxItems):base(name)
    {

        /* if (TContainer is derived from Swag) { TContents must be too } */

        _contents = new ContainerContents<TContents>(maxItems);
    }
}

public class ContainerContents<T> : List<T> where T : BaSEObject
{
    int _maxItems;

    public ContainerContents(int maxItems)
    {
        _maxItems = maxItems;
    }
}

interface ICarryable { }
interface IContainer<T> { }

class Backpack<T> : ICarryable,IContainer<T>
where T : ICarryable 
{  }

class Vault<T> : IContainer<T>
{  }