Asp.Net MVC3 Singleton变量

Question

It is chance define some singleton variable in asp.net mvc3 ? I want define it (probably in global.asax) and then in controllers get it, by IOC resolver (structureMap)

Simple: I want have one property with same data for all users, not dependency on request, session, ... For example At first start of MVC application I set DateTime value into this property and then all requests can view this property and modified this property in controllers.

Answer 1

Just use StructureMap to create your controllers using a dependency resolver like outlined in this blog post . Inject not the variable directly but an instance that holds that variable:

public class GlobalScope 
{
  public String Variable { get; set; }
}

Now you can inject GlobalScope into your controllers and set/get the Variable but keep in mind that you're in a multi threaded environment where read and write access to variables must be synchronized or you run into some weird race conditions.

Answer 2

First of all you can use simple singleton pattern in .net wihich is not related to asp.net or asp.net mvc specific things at all.

If you want to use IoC, you can register you class instance like single instance and IoC will return you always only single class instance. Put necessary properties to this instance and edit it. Initialization will be on the type registration step:

Sample in Autofac :

builder.Register(MySingleton.Instance);

and with Lazy initialization:

builder.Register(c => MySingleton.Instance);

Also you can register type and IoC will control your type initialization, but in this case you can't set your default value during initialization:

builder.RegisterType<MyType>().SingleInstance();

Answer 3

Any Variable or class that is public Static resides in the AppDomain and is globally availiable for use in all sessions. So you could simply:

• Create a Public Static Class Called "CurrentApplication" in APP_CODE and then use it in all sessions.
• Also IOC works great for this as well because most IOC object default Lifestyle is Singleton and therefore resides in the AppDomain as well.
• Another way could be to use a "Common Service locator"

Have been known to use all 3 including using a Common Service Location to find the IOC container, which makes life so easy.

Hope this Helps

Answer 4

You could store the data as a static member of the Application class. See this article - Application State in ASP.NET

Answer 5

Your IoC container probably extends the concept of a singleton. Ninject does with InSingletonScope. This would work better than a static app variable as any libraries would have to know about your application, and then you have circular references.