Generic Singleton - any suggestions?

[Andrew Ducker]

I want to make a whole bunch of classes into singletons. They all
descend from a base class.

I'd like to have code in the base class along the lines of :
private This(){ }
private static readonly This instance = new This();
public static This Instance
{
get
{
return instance;
}
}

but there's no way to get the type of the current class and use that
as the equivalent of a generic.

Any suggestions?

Andy

 

[Nicholas Paldino [.NET/C# MVP]]

Jon Skeet's article on implementing a singleton can easily be adapted to
use generics. Just make sure that the type T has a constraint of new so
that you can create the instance. Here is the link:

http://www.yoda.arachsys.com/csharp/singleton.html

 

[Marc Gravell]

Jon Skeet's article on implementing a singleton can easily be

adapted to use generics. Just make sure that the type T has a
constraint of new so that you can create the instance.

But if it qualifies for "new()", I'm not sure you can really say it is
a singleton in the strictest sense - just that there is a static
instance available.

Marc

 

[Andrew Ducker]

But if it qualifies for "new()", I'm not sure you can really say it is
a singleton in the strictest sense - just that there is a static
instance available.

Yeah, that was my problem. I could do all of it bar enforcing it
being an actual singleton.

Andy

 

[Jon Skeet [C# MVP]]

Yeah, that was my problem. I could do all of it bar enforcing it
being an actual singleton.

I don't believe there's any way of achieving what you want particularly
easily.

However, you can make the singleton pattern *really* short by using a
field rather than a property:

public class Singleton
{
public static readonly Singleton Instance = new Singleton();

Singleton(){}
}

As it's read-only, it's not violating encapsulation very much. You
can't use it for databinding, or put a breakpoint on it, but many of
the other disadvantages of exposing fields don't really apply. (As an
example of this being done in the framework, String.Empty is a field.)