QuickTip: Use CommonServiceLocator and MvcServiceLocator together in ASP.NET MVC 3 Pre-Release Projects

Sep 23 2010

UPDATE: This post is outdated since ASP.NET MVC Beta.  Use the DependencyResolver static class instead.

The integration of the CommonServiceLocator pattern within ASP.NET MVC is a positive step forward for the .MVC framework. Dependency management via ServiceLocation is a smart way to go, especially for large codebases with complex dependency needs. ServiceLocation keeps constructors clean, and prevents bloat in higher-level classes which don’t need to know about lower-level dependencies.

However, the fact that .MVC now has its own ServiceLocation infrastructure, via the System.Web.Mvc.IServiceLocator interface, is a little troublesome for code which already uses the Microsoft CommonServiceLocator class found in the Unity Enterprise Application Block. But don’t fret- luckily, the IServiceLocator interface is exactly the same in the System.Web.Mvc namespace and the Microsoft.Practices.ServiceLocation namespace. This means you can have one class implement both interface simultaneously, like so:

public class  SomeServiceLocatorWrapper : System.Web.Mvc.IServiceLocator, Microsoft.Practices.ServiceLocation.IServiceLocator
{
 //Implicity Implementation of Methods
}

What’s even easier is when there’s already a wrapper class around the IServiceLocator for you, such as the one provided by Unity via the UnityServiceLocator class in Microsoft.Practices.Unity’s namespace. The following code below provides all the functionality you need to use both ServiceLocators:

public class UnityMvcServiceLocator : UnityServiceLocator, System.Web.Mvc.IServiceLocator
{
 public UnityMvcServiceLocator(IUnityContainer container)
 : base(container)
 {

 }

}

Once you have that class in place, then it’s just a matter of hooking both up in your Global.asax file like so:

//In Global.asax's Application_Start hook:
var container = UnityContainerBuilder.CreateContainer();
var locator = new UnityMvcServiceLocator(container);

ServiceLocator.SetLocatorProvider(() => locator);
MvcServiceLocator.SetCurrent(locator);

This allows you to access the same locator either via the MvcServiceLocator.Current instance or the ServiceLocator.Current instance.