UnityContainerExtensions.Resolve(this IUnityContainer container, Type t, string name, params ResolverOverride[] overrides) seems to be missing about container

[JesperRisager]

I played a bit more with it and discovered the following:

var container = new UnityContainer();
return container.Resolve(serviceType, key); // Does not compile

var iContainer = (IUnityContainer) new UnityContainer();
return iContainer.Resolve(serviceType, key); // Does compile

So as long as you use the IUnityContainer interface it works fine, but if you use the UnityContainer directly, you get into the problem of the missing extension method.

To continue with the upgrade I simply started using the IUnityContainer interface to resolve with everywhere and now it all works.