How to get HttpContext.Current in ASP.NET Core?

Question

We are currently rewriting/converting our ASP.NET WebForms application using ASP.NET Core. Trying to avoid re-engineering as much as possible.

There is a section where we use HttpContext in a class library to check the current state. How can I access HttpContext.Current in .NET Core 1.0?

 var current = HttpContext.Current;
     if (current == null)
      {
       // do something here
       // string connection = Configuration.GetConnectionString("MyDb");
      }

I need to access this in order to construct current application host.

$"{current.Request.Url.Scheme}://{current.Request.Url.Host}{(current.Request.Url.Port == 80 ? "" : ":" + current.Request.Url.Port)}";

Answer 1

As a general rule, converting a Web Forms or MVC5 application to ASP.NET Core will require a significant amount of refactoring.

HttpContext.Current was removed in ASP.NET Core. Accessing the current HTTP context from a separate class library is the type of messy architecture that ASP.NET Core tries to avoid. There are a few ways to re-architect this in ASP.NET Core.

HttpContext property

You can access the current HTTP context via the HttpContext property on any controller. The closest thing to your original code sample would be to pass HttpContext into the method you are calling:

public class HomeController : Controller
{
    public IActionResult Index()
    {
        MyMethod(HttpContext);

        // Other code
    }
}

public void MyMethod(Microsoft.AspNetCore.Http.HttpContext context)
{
    var host = $"{context.Request.Scheme}://{context.Request.Host}";

    // Other code
}

HttpContext parameter in middleware

If you're writing custom middleware for the ASP.NET Core pipeline, the current request's HttpContext is passed into your Invoke method automatically:

public Task Invoke(HttpContext context)
{
    // Do something with the current HTTP context...
}

HTTP context accessor

Finally, you can use the IHttpContextAccessor helper service to get the HTTP context in any class that is managed by the ASP.NET Core dependency injection system. This is useful when you have a common service that is used by your controllers.

Request this interface in your constructor:

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

You can then access the current HTTP context in a safe way:

var context = _httpContextAccessor.HttpContext;
// Do something with the current HTTP context...

IHttpContextAccessor isn't always added to the service container by default, so register it in ConfigureServices just to be safe:

public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpContextAccessor();
    // if < .NET Core 2.2 use this
    //services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();

    // Other code...
}

Answer 2

Necromancing.
YES YOU CAN, and this is how.
A secret tip for those migrating large junks chunks of code:
The following method is an evil carbuncle of a hack which is actively engaged in carrying out the express work of satan (in the eyes of .NET Core framework developers), but it works:

In public class Startup

add a property

public IConfigurationRoot Configuration { get; }

And then add a singleton IHttpContextAccessor to DI in ConfigureServices.

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<Microsoft.AspNetCore.Http.IHttpContextAccessor, Microsoft.AspNetCore.Http.HttpContextAccessor>();

Then in Configure

    public void Configure(
              IApplicationBuilder app
             ,IHostingEnvironment env
             ,ILoggerFactory loggerFactory
    )
    {

add the DI Parameter IServiceProvider svp, so the method looks like:

    public void Configure(
           IApplicationBuilder app
          ,IHostingEnvironment env
          ,ILoggerFactory loggerFactory
          ,IServiceProvider svp)
    {

Next, create a replacement class for System.Web:

namespace System.Web
{

    namespace Hosting
    {
        public static class HostingEnvironment 
        {
            public static bool m_IsHosted;

            static HostingEnvironment()
            {
                m_IsHosted = false;
            }

            public static bool IsHosted
            {
                get
                {
                    return m_IsHosted;
                }
            }
        }
    }


    public static class HttpContext
    {
        public static IServiceProvider ServiceProvider;

        static HttpContext()
        { }


        public static Microsoft.AspNetCore.Http.HttpContext Current
        {
            get
            {
                // var factory2 = ServiceProvider.GetService<Microsoft.AspNetCore.Http.IHttpContextAccessor>();
                object factory = ServiceProvider.GetService(typeof(Microsoft.AspNetCore.Http.IHttpContextAccessor));

                // Microsoft.AspNetCore.Http.HttpContextAccessor fac =(Microsoft.AspNetCore.Http.HttpContextAccessor)factory;
                Microsoft.AspNetCore.Http.HttpContext context = ((Microsoft.AspNetCore.Http.HttpContextAccessor)factory).HttpContext;
                // context.Response.WriteAsync("Test");

                return context;
            }
        }


    } // End Class HttpContext 


}

Now in Configure, where you added the IServiceProvider svp, save this service provider into the static variable "ServiceProvider" in the just created dummy class System.Web.HttpContext (System.Web.HttpContext.ServiceProvider)

and set HostingEnvironment.IsHosted to true

System.Web.Hosting.HostingEnvironment.m_IsHosted = true;

this is essentially what System.Web did, just that you never saw it (I guess the variable was declared as internal instead of public).

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IServiceProvider svp)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    ServiceProvider = svp;
    System.Web.HttpContext.ServiceProvider = svp;
    System.Web.Hosting.HostingEnvironment.m_IsHosted = true;


    app.UseCookieAuthentication(new CookieAuthenticationOptions()
    {
        AuthenticationScheme = "MyCookieMiddlewareInstance",
        LoginPath = new Microsoft.AspNetCore.Http.PathString("/Account/Unauthorized/"),
        AccessDeniedPath = new Microsoft.AspNetCore.Http.PathString("/Account/Forbidden/"),
        AutomaticAuthenticate = true,
        AutomaticChallenge = true,
        CookieSecure = Microsoft.AspNetCore.Http.CookieSecurePolicy.SameAsRequest

       , CookieHttpOnly=false

    });

Like in ASP.NET Web-Forms, you'll get a NullReference when you're trying to access a HttpContext when there is none, such as it used to be in Application_Start in global.asax.

I stress again, this only works if you actually added

services.AddSingleton<Microsoft.AspNetCore.Http.IHttpContextAccessor, Microsoft.AspNetCore.Http.HttpContextAccessor>();

like I wrote you should.
Welcome to the ServiceLocator pattern within the DI pattern ;)
For risks and side effects, ask your resident doctor or pharmacist - or study the sources of .NET Core at github.com/aspnet, and do some testing.

---

Perhaps a more maintainable method would be adding this helper class

namespace System.Web
{

    public static class HttpContext
    {
        private static Microsoft.AspNetCore.Http.IHttpContextAccessor m_httpContextAccessor;


        public static void Configure(Microsoft.AspNetCore.Http.IHttpContextAccessor httpContextAccessor)
        {
            m_httpContextAccessor = httpContextAccessor;
        }


        public static Microsoft.AspNetCore.Http.HttpContext Current
        {
            get
            {
                return m_httpContextAccessor.HttpContext;
            }
        }


    }


}

And then calling HttpContext.Configure in Startup->Configure

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IServiceProvider svp)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();


    System.Web.HttpContext.Configure(app.ApplicationServices.
        GetRequiredService<Microsoft.AspNetCore.Http.IHttpContextAccessor>()
    );

Answer 3

There is a solution to this if you really need a static access to the current context. In Startup.Configure(….)

app.Use(async (httpContext, next) =>
{
    CallContext.LogicalSetData("CurrentContextKey", httpContext);
    try
    {
        await next();
    }
    finally
    {
        CallContext.FreeNamedDataSlot("CurrentContextKey");
    }
});

And when you need it you can get it with :

HttpContext context = CallContext.LogicalGetData("CurrentContextKey") as HttpContext;

I hope that helps. Keep in mind this workaround is when you don’t have a choice. The best practice is to use de dependency injection.