Comments on: Service Locator Pattern in C# with Lazy Initialization

By: Anonymous

Anonymous — Sat, 17 Sep 2011 12:02:00 +0000

Yes, that should work as well. Remember the goal of this post is to show a simple example, not to re-write a full fledged IOC container.

By: Istace Emmanuel

Istace Emmanuel — Fri, 02 Sep 2011 23:59:00 +0000

I’m using Activator.CreateInstance(T); on the GetService(T) and i store pair of Interface/ImplementationType into the dictionnary. Sound it as a good solution ?

By: Anonymous

Anonymous — Thu, 11 Aug 2011 07:16:00 +0000

Lazy has been introduced with .NET 4, which had not been released yet at the time of writing this post.

By: Foo

Foo — Thu, 11 Aug 2011 04:20:00 +0000

why not use Lazy ?

By: LegoMyEgo

LegoMyEgo — Wed, 03 Aug 2011 19:31:00 +0000

I tried using this method of constraining the Generic type to class, new() and it doesnt work because when using the GetService the T your usually passing in an Interface. So.. the interface is an abstract type with no constructor.. so this does not work. The example he has given the the blog works fine.. but your implementation here fails.

By: Anonymous

Anonymous — Wed, 17 Nov 2010 07:34:00 +0000

Phill,

thank you for your comment. Your solution seems to be cleaner and more
efficient.

By: Phill

Phill — Tue, 16 Nov 2010 22:32:00 +0000

There is no need to go to that much trouble… by adding a new() constraint to your generic parameter then you can insure that they have a default constructor and call that directly:

public T GetService() : where T : class, new()
19 {
20 if (this.instantiatedServices.ContainsKey(typeof(T)))
21 {
22 return (T)this.instantiatedServices[typeof(T)];
23 }
24 else
25 {
26
33 T service = new T();
34
35 // add the service to the ones that we have already instantiated
36 instantiatedServices.Add(typeof(T), service);
37
38 return service;
39 }
40 catch (KeyNotFoundException)
41 {
42 throw new ApplicationException”The requested service is not registered”);
43 }
44 }
45 }

Note, there may be some errors in that but the concept is sound.

By: Alex Goldman

Alex Goldman — Sun, 02 May 2010 07:26:52 +0000

Hi,

There is small problem using Dictionary, Some times custom class that you create new instance they inherit several interfaces.

I using IList : TheList.OfType(the Interface)

By: Alex Goldman

Alex Goldman — Sun, 02 May 2010 07:26:00 +0000

Hi,

There is small problem using Dictionary, Some times custom class that you create new instance they inherit several interfaces.

I using IList : TheList.OfType(the Interface)

By: Cameron

Cameron — Wed, 17 Mar 2010 20:50:22 +0000

“It would be interesting to investigate whether mature service locator implementations (Castle Windsor, Spring.NET, StructureMap, etc…) have tackled this kind of problem and how they solved it.”

I think they use weak references (http://msdn.microsoft.com/en-us/library/system.weakreference.aspx)
But I guess that’s the benefit of having a custom service locator class – if you don’t need the logic for instance lifetime management then you can leave it out.