Using Unity to create a singleton that is used in my Class

Question

I have a class that needs an instance of a HttpClient class, which I want to be instantiated only once i.e. Singleton

public interface IMyClass {}
public class MyClass : IMyClass {
    private HttpClient client;
    public MyClass(HttpClient client)
    {
        this.client = client;
    }
}


IUnityContainer container = new UnityContainer();
container.RegisterType<IMyClass, MyClass>();

var httpClient = new HttpClient();

How can I register the httpClient instance as a singleton to my MyClass can use it?

@Itsik Most likely because HTTP client was designed to be used as a singleton. I personally don't recommend using it per-request. — Vlad Stryapko
– Vlad Stryapko, Commented Jul 4, 2017 at 19:00

Vlad Stryapko · Accepted Answer · 2017-07-04 19:08:48Z

3

Have you tried this?

container.RegisterType<IMyClass, MyClass>(new ContainerControlledLifetimeManager());

https://msdn.microsoft.com/en-us/library/ff647854.aspx

Since there will be only one instance of your class, there will also one only one instance of HTTP client inside it.

Update:

In order to resolve HttpClient dependency itself, use

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

That way any class that needs HttpClient will receive the same instance of it. I'm not sure about the order of parameters, but basically you have to tell Unity 2 things - to register HttpClient as a singleton and to use its default constructor.

edited Jul 4, 2017 at 19:08

answered Jul 4, 2017 at 18:52

Vlad Stryapko

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8 Comments

cool breeze Over a year ago

I want to use HttpClient in other classes also, not just in MyClass.

cool breeze Over a year ago

I don't see you registering the class HttpClient anywhere? How would that work?

Vlad Stryapko Over a year ago

Would you like it to be Singleton for all classes or a separate instance for each of them?

cool breeze Over a year ago

Singleton for all classes that need a HttpClient.

Vlad Stryapko Over a year ago

It's because Unity tries to create HttpMessageHandler for you. You can specify the constructor directly using new InjectionConstructor() inside RegisterType to use a parameterless one.

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