public abstract class ExtensionIdProvider<T> : IExtensionId<T>, 
	IExtensionId
where T : IExtension

Public MustInherit Class ExtensionIdProvider(Of T As IExtension)
	Implements IExtensionId(Of T), IExtensionId

generic<typename T>
where T : IExtension
public ref class ExtensionIdProvider abstract : IExtensionId<T>, 
	IExtensionId

[<AbstractClassAttribute>]
type ExtensionIdProvider<'T when 'T : IExtension> =  
    class
        interface IExtensionId<'T>
        interface IExtensionId
    end