Access to HTTPContext

Question

I have built REST API in Net Core 2.1

The project is divided into Assemblies:

APIREST (includes controllers)
MODULES (modules containing logic and repositories)

Can I use HTTPContext correctly in the modules to download the saved UserId in JWT?

The query for the database requires information about UserId in the token on the query

I know that when I call in the scope of the controller's code I will get the correct value but will I also get it in another assembly in a different class?

When the scope of the query ends, is the HTTPContext content removed?

Why would a business logic module need to know that it's being run in an HTTP context? Why would you inject the HttpContext in a business logic class, only for that class to extract a JWT and resolve that to a UserId? Why not pass the UserId from the controller to the business logic? Also, please read [ask] and share your research. — CodeCaster, Jul 08 '19 at 12:11
See for example [How do I get current user in .NET Core Web API (from JWT Token)](https://stackoverflow.com/questions/46112258/how-do-i-get-current-user-in-net-core-web-api-from-jwt-token), [Access the current HttpContext in ASP.NET Core](https://stackoverflow.com/questions/31243068/access-the-current-httpcontext-in-asp-net-core) and many others. — CodeCaster, Jul 08 '19 at 12:12
@CodeCaster At the moment I am sending UserId to the repository via a function prepared for it directly from the controller. And I wonder if I could skip this and download the UserId from HTTPContext directly in the module — NetDev, Jul 08 '19 at 12:14
wouldn't it be simpler to inject the userid param in the business logic class? — Aamir Masood, Jul 08 '19 at 12:20

score 2 · Answer 1 · answered Jul 08 '19 at 13:12

HttpContext has a scoped lifetime and is dependency injected now. In places where you do not have access to it out of the box (controllers/pages/views), you can inject IHttpContextAccessor, which is a singleton that knows how to retrieve the HttpContext instance in scope.

public class MyClass
{
    private readonly IHttpContextAccessor _httpContextAccessor;

    public MyClass(IHttpContextAccessor httpContextAccessor)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    public void MyMethod()
    {
        var userId = _httpContextAccessor.HttpContext?.User.FindFirstValue(ClaimTypes.NameIdentifier);
        if (userId != null)
        {
            // do something
        }
    }
}

HttpContext could potentially be null, so you need to handle that with a null check.

You will of course need to register MyClass with the service collection, and you'll need to inject it, as well, when you need it, or none of this will work. Additionally, IHttpContextAccessor is not included by default, as there's a non-neglible performance impact. You will need to add the following line to your app's ConfigureServices, if you want to use it:

services.AddHttpContextAccessor();

Now, all that said, pretty much forget everything I just told you. Don't actually do this. A well-designed class should follow the principles of SOLID, one of which is that it should do just one thing and do it well. In the majority of cases, it's completely inappropriate for a class in some library to have knowledge of something like HttpContext.

Instead, if you need the user id in some method, simply pass it in to that method:

public void DoSomethingWithUserId(string userId)

Then, in your controller, for example, where you already have access to HttpContext:

myClass.DoSomethingWithUserId(User.FindFirstValue(ClaimTypes.NameIdenfiier));

Access to HTTPContext

1 Answers1