initialize objects in ASP.custom middleware and inject them - asp.net-web-api

Question

I have an ASP.NET Core Web API which reads an auth token in the request header and decodes the values in it.
I have written custom middleware to decode the token. I have also created a UserContext object to hold the values decoded from the token and I'm setting the decoded values into the UserContext object.
I now want to be able to inject the UserContext object (which was created inside the custom middleware) into my contollers, and I'm unable to figure out how to do that.
Please help.

Answer 1

You can use the HttpContext.Items
In your middleware you will have access to the HttpContext, ofcourse
You can store your user context in the items dictionary which is transient and scoped to the lifetime of one http request. Below is an example middleware where 'context' is the Http context object. You will have this object in your middleware.
app.Use(async (context, next) =>
{
context.Items.Add("UserContext", new UserContext());
await next.Invoke();
});
You can then access the HttpContext in your controller by injecting the IHttpContextAccessor object.
public class ApiController : Controller
{
public readonly IHttpContextAccessor _context;
public ApiController(IHttpContextAccessor context)
{
_context = context;
}
public IActionResult Get()
{
// Get the http context
UserContext userContext = (UserContext) _context.HttpContext.Items["UserContext"];
return Ok();
}
}
From the IHttpContextAccessor, you can get the HttpContext object, and from that you can get the Items dictionary.
Of course, do some checking to see if the key "UserContext" exists but I think this will work for you
EDIT
Because you will want to pass it to other repository/services.
Instead of passing the HttpContextAccessor to all of them, which you can do. Create a service the encapsulates the creation of the UserContext object.
It can look something like this.
public interface IRepositry { }
public class Repositry : IRepositry
{
private IUserContextService _userContextService;
public Repositry(IUserContextService userContextService)
{
_userContextService = userContextService;
}
}
public class UserContext
{
}
public interface IUserContextService
{
UserContext GetUser();
}
public class UserContextService : IUserContextService
{
private readonly IHttpContextAccessor _context;
public UserContextService(IHttpContextAccessor context)
{
_context = context;
}
public UserContext GetUser()
{
var token = _context.HttpContext.Request.Headers["UserToken"];
// do something with the token to create the UserContext;
return new UserContext();
}
}
Create a UserContextService that reads from the HttpContext. Make the UserContextService a singleton but when you get the user, always return a new UserContext, this is because you of course in a multi-threaded environment and you never want to persist this object because you may end up reading someone else's UserContext, so always return new. Register this service in your ConfigureServices method in your startup class .
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<IUserContextService, UserContextService>();
services.AddSingleton<IRepositry, Repositry>(serviceCollection => new Repositry(serviceCollection.GetService<IUserContextService>()));
}
You can then inject your repository to your API controller for example
public class ApiController : Controller
{
public readonly IRepositry _repositry;
public ApiController(IRepositrycontext repositry)
{
_repositry= repositry;
}
public IActionResult Get()
{
// Get the http context
return Ok();
}
}