'宣言 Public MustInherit Class DropDownBuilder (Of T,TControl As DropDown(Of T), TBuilder As DropDownBuilder(Of T,TControl,TBuilder)) Inherits ItemsBoundControlBuilder(Of T,TControl,TBuilder)
public abstract class DropDownBuilder<T,TControl,TBuilder> : ItemsBoundControlBuilder<T,TControl,TBuilder> where TControl: DropDown<T> where TBuilder: DropDownBuilder<T,TControl,TBuilder>