Hi, I've just stumbled upon this: within a Unity container, I want to register IDictionary<TK, TV>; assume that it's IDictionary<string, int> _unityContainer = new UnityContainer() .RegisterType<IDictionary<string, int>, Dictionary<string, int>>(); but if I try var d = _unityContainer.Resolve<IDictionary<string, int>>(); it fails to resolve... I get... Microsoft.Practices.Unity.ResolutionFailedException: Microsoft.Practices.Unity.ResolutionFailedException: Resolution of the dependency failed, type = "System.Collections.Generic.IDictionary`2[System.String,System.Int32]", name = "(none)". Exception occurred while: while resolving. Exception is: InvalidOperationException - The type Dictionary`2 has multiple constructors of length 2. Unable to disambiguate. At the time of the exception, the container was: Resolving System.Collections.Generic.Dictionary2[System.String,System.Int32],(none) (mapped from System.Collections.Generic.IDictionary2[System.String,System.Int32], (none)) --- System.InvalidOperationException: The type Dictionary`2 has multiple constructors of length 2. Unable to disambiguate.. So it looks like it has found the Type to resolve (being Dictionary<string, int>) but failed to new it up... How come unity can't resolve this type? If I type IDictionary<string, int> d = new Dictionary<string, int>() that works... any ideas? thanks!