Longing to know

In the solution that I’m migrating to ASP.NET Core, I have a domain project that uses System.Web’s HttpContext. Since System.Web is not part of .NET Core, I had to figure out how one gets the current user’s identity within a domain class.

Fortunately, with .NET Core’s built-in DI, this is pretty easy. HttpContext access has been abstracted into a set of abstractions (yeah, that sounds redundant) in this package:

"Microsoft.AspNetCore.Http.Abstractions": "1.0.0"

Once this package is added to the domain project, the constructor of whatever class that needs HttpContext needs to be modified. My class is called CurrentUserService. The constructor and a few private accessors are all that are needed. Then, we can access the User and Identity objects from the HttpContext.

private IHttpContextAccessor _contextAccessor;
private HttpContext _context { get { return _contextAccessor.HttpContext; } }

public CurrentUserService(IHttpContextAccessor contextAccessor)
{
    _contextAccessor = contextAccessor;
}

public string UserName
{
    get
    {
        var userName = "SystemGenerated";
        // Figure out the user's identity
        if (_context != null)
        {
            if (_context.User != null)
            {
                var identity = _context.User.Identity;

                if (identity != null && identity.IsAuthenticated)
                {
                    userName = identity.Name;
                }
            }
        }

        return userName;
    }

While the code above shows getting the Name for the current identity, we could also access any claim by casting the Identity to a ClaimsIdentity.

In the web project, the IHttpContextAccessor needs to be specified for injection as a transient singleton so that we get one per request. This is performed in the Startup.cs’s ConfigureServices method.

* Update: IHttpContextAccessor should be registered as a singleton. If it’s not registered as a singleton, you will have unpredictable behavior.

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

After making these changes, the ported domain project’s code works as expected.