IUnityContainer.Resolve<T> throws error claiming it cannot be used with type parameters

Question

Yesterday I've implemented the code:

CustomerProductManager productsManager = container.Resolve<CustomerProductManager>();

It was compilable and working.

Today (probably I've modified something) I am constantly getting the error:

The non-generic method 'Microsoft.Practices.Unity.IUnityContainer.Resolve(System.Type, string, params Microsoft.Practices.Unity.ResolverOverride[])' cannot be used with type arguments

My collegue has the same source code and doesn't have same error. Why? How to resolve the problem?

P.S.

line "using Microsoft.Practices.Unity;" is present in usings section.

I've tried to replace generic version with non-generic one:

CustomerProductManager productsManager = (CustomerProductManager)container.Resolve(typeof(CustomerProductManager));

And got another error:

No overload for method 'Resolve' takes '1' arguments

It seems like one of the assemblies is not referenced.. but which one? I have 2 of them referenced: 1. Microsoft.Practices.Unity.dll 2. Microsoft.Practices.ServiceLocation.dll

P.P.S. I've saw similar problem http://unity.codeplex.com/WorkItem/View.aspx?WorkItemId=8205 but it is resolved as "not a bug"

Any thought will be helpful

Lugsail

Are you using Unity 2.0? – Selfcontradiction

You'll probably find that it's the Power Commands add-on that's removing unused namespace using clauses; the namespace is "unused" when your code is in an uncompilable state and you probably have a habit of saving the file during editing--and the add-on removes the extra uses when saving. – Althaalthea

Answer 1

I had the same problem and found the "fix" looking at Prism sample code files. Looks like, even if it is not a dll in Unity V2 you have to add a reference in your class to: Microsoft.Practices.Unity

my complete "using" section is as follow

using System;
using System.Windows;
using Microsoft.Practices.Composite.Modularity;
using Microsoft.Practices.Unity;
using Microsoft.Practices.Composite.UnityExtensions;

I'm not sure if you are using Silverlight, but the generic version for Container.Resolve IS in Microsoft.Practices.Unity.

Insignificancy

Exactly. Some time ago I've detected that adding 'using Microsoft.Practices.Unity;' resolves an issue. – Lugsail

This worked me also, but damn resharper is now moaning about unused 'using directives.' – Clifford

The reason is that Resolve with a type parameter is an extension method found in Microsoft.Practices.Unity, while the Resolve() without a type parameter is just a method on the interface (or class). – Carlson

Thx! All these years later and this just happened on brand new code. HttpClient is the same way with these 'hidden' extension secrets. Not a fan. I like Simple Injector. – Battleplane

Worked for me. Weird thing was I could go to the definition fine but the using statement wasn't there. – Sentry

And FWIW, in the new and supposedly highly compatible Unity 5, the namespace is now Unity and not Microsoft.Practices.Unity. – Kaspar

Thx Ken, you saved me a ton of time trying to track this down. Upgraded my Unity nuget package and this no longer worked until just changing to using Unity like you mentioned – Electroshock

Thanks, I was totally confused with - Resolve(Type type, string name, params ResolverOverride[] overrides) – Histopathology

Answer 2

Microsoft no longer owns Unity and it's in version 5, the namespace is now:

using Unity;

Ensure that is in your using section when using:

container.Resolve<T>();

Rives

Note that in case you're using Prism, the current stable version (6.3.0) of Prism still uses Unity 4.0.1, where you still have to using Microsoft.Practices.Unity; – Emmittemmons

Seriously, this one was driving me nuts. Thanks! – Mumble

Answer 3

I faced this problem and none of this answers did not help me. I was getting the compile time error

Unknown method RegisterType() of Microsoft.Practices.Unity.IUnityContainer

for my below code.

Container.RegisterType<IMyInterface, MyClass>();

I found that if you did not implement IMyInterface to the class MyClass, you get this issue. Hope it resolves for you too...

Hierodule

Answer 4

In my situation the class I was wrapping with Unity inherited from an abstract base class, and that base class did NOT have a parameterless constructor. Once I changed my code to use a parameterless constructor for the base class, the problem disappeared.

Racialism

Answer 5

In my situation, I had Bootstrapper implement its own Resolve without the generic version, so it couldn't find the Microsoft's Unity Resolve. Adding the proper usings did the trick.

Bahaism