public abstract class Singleton<T>
where T : new(), Singleton<T>

Public MustInherit Class Singleton(Of T As {New, Singleton(Of T)})

generic<typename T>
where T : gcnew(), Singleton<T>
public ref class Singleton abstract

[<AbstractClassAttribute>]
type Singleton<'T when 'T : new() and Singleton<'T>> =  class end

public class Log : Singleton<Log>
{
  ...
}

var log = Log.Instance;
var log = Singleton<Log>.Instance;