如何从基类泛型派生泛型类？

Question

我有一个抽象基类通用

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

    protected abstract void Method(); 

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

B级从A派生类型的TreeView

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

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

    } 
} 

如何从B级与从TreeView的派生类型派生？

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

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

    } 
} 

Answer 1

，而不是具体类TreeView添加通用约束：

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

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

    } 
}