How to configure HttpClient via Unity container?

Question

I'm trying to register an instance of HttpClient object with the unity container so that it can be used throughout the app, but running into the error - "The type HttpMessageHandler does not have an accessible constructor."

Here is the code I use to register the HttpClient with Unity-

private static IUnityContainer BuildUnityContainer()
    {
        var container = new UnityContainer();

        container.RegisterType<HttpClient>(
            new InjectionProperty("BaseAddress", new Uri(ConfigurationManager.AppSettings["ApiUrl"]))); 

        return container;
    }

Apparently Unity tries to create the `HttpClient` using the `HttpClient(HttpMessageHandler)` or `HttpClient(HttpMessageHandler, Boolean)` constructor. `HttpMessageHandler` is an abstract class, so it can't create an instance of it. — dtb, Feb 04 '13 at 22:46

score 12 · Accepted Answer · edited Aug 09 '18 at 19:29

12

You can use the factory method to register it instead:

container.RegisterType<HttpClient>(
    new InjectionFactory(x => 
        new HttpClient { BaseAddress = new Uri(ConfigurationManager.AppSettings["ApiUrl"]) }
    )
);

edited Aug 09 '18 at 19:29

birwin

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answered Feb 05 '13 at 08:30

jgauffin

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2

This worked great, minor mistake is that BaseAddress takes in Url instead of string – camelCaseWarrior Feb 05 '13 at 17:15

score 9 · Answer 2 · edited Feb 01 '23 at 14:48

9

By default Unity uses the constructor with the most parameters. That would be HttpClient(HttpMessageHandler, Boolean) in your case. You need to explicitly specify the parameterless default ctor.

container.RegisterType<HttpClient>(
    new InjectionProperty(...), 
    new InjectionConstructor());

edited Feb 01 '23 at 14:48

ruffin

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answered Feb 05 '13 at 08:14

Sebastian Weber

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Good to know, and it did work. How would we add DefaultRequestHeaders with this InjectionProperty/InjectionConstructor style of configuring? With InjectionFactory it was do-able. – camelCaseWarrior Feb 05 '13 at 17:17
@RubberDuckDuck You can add multiple `InjectionProoperties` if you want to. And you can add parameters to the `InjectionConstructor` as well. You have to add all parameters the constructor takes in the correct order. If you want the container to resolve some of those parameters you can add the parameters `Type` as some kind of wildcard. – Sebastian Weber Feb 05 '13 at 19:57

How to configure HttpClient via Unity container?

2 Answers2