CODEWITHSUNDEEP
asp.net-core-mvc
Dave Van den Eynde
Dave Van den Eynde

Reputation: 17445

How do I resolve a dependency during ConfigureServices?

Given this example implementation of ConfigureServices:

public void ConfigureServices(IServiceCollection services)
{           
    services.AddSingleton<SomeComponent>();

    services.AddMvc(config =>
    {
        config.OutputFormatters.Add(new CustomFormatter(/* HELP! */));
    });
}

I need to pass an instance of SomeComponent (hopefully only a single one will exist) to the constructor of my custom formatter. How can resolve such an instance from within the ConfigureServices implementation?

Upvotes: 1

Views: 385

Answers (2)

Will Ray
Will Ray

Reputation: 10889

You can build the service provider in advance and use it like this:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<SomeComponent>();

    var provider = services.BuildServiceProvider();
    var item = provider.GetService<SomeComponent>();

    services.AddMvc(config =>
    {
        config.OutputFormatters.Add(new CustomFormatter(item));
    });
}

Upvotes: 2

RonC
RonC

Reputation: 33897

I know that some developers see the service locator pattern as an anti-pattern. But there are cases where it's the right tool for the job. This is probably one of those cases. You could solve your issue like so:

public void ConfigureServices(IServiceCollection services, 
                              IHttpContextAccessor contextAccessor)
{           
    services.AddSingleton<SomeComponent>();

    var someComponent = contextAccessor.HttpContext.RequestServices.GetServices<SomeComponent>(); //service locator pattern
    services.AddMvc(config =>
    {
        config.OutputFormatters.Add(new CustomFormatter(someComponent));
    });
}

The above example is for RC2 I notice that in RC1 the key line is a bit different and would be like this:

var someComponent = contextAccessor.HttpContext.ApplicationServices.GetService<SomeComponent>();

Upvotes: 1

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