如何從基礎泛型類派生泛型類？

Question

我有一個基本的抽象泛型類

public abstract class A<T> where T: Control
{
    protected T _t { get; set; }

    protected abstract void Method ();

    protected A(T t)
    {
        _t = t;
    }
}

B類是從A派生的，其類型為TreeView

public class B<T>: A<TreeView>
{
    protected override void Method ()
    {
        _t.CallSomeTreeViewMethod (); // ok!
    }

    public B (TreeView tree): base (tree)
    {

    }
} 

如何從B類派生具有從TreeView派生的類型？

public class C: B<ExtendedTreeView>
{
    protected override void Method ()
    {
        _t.CallSomeExtendedTreeViewMethod ();
    }

    public C (ExtendedTreeView tree): base (tree)
    {

    }
}

Answer 1

代替具體的類TreeView添加通用約束：

public class B<T>: A<T> where T:TreeView
{
    protected override void Method ()
    {
        _t.CallSomeTreeViewMethod (); // ok!
    }

    public B (T tree): base (tree)
    {

    }
}