AspNetCore.Docs/aspnetcore/fundamentals/http-context.md

---
title: Access HttpContext in ASP.NET Core
author: coderandhiker
description: Learn how to access HttpContext in ASP.NET Core.
ms.author: riande
ms.custom: mvc
ms.date: 07/27/2018
uid: fundamentals/httpcontext
---
# Access HttpContext in ASP.NET Core

ASP.NET Core apps access the `HttpContext` through the [IHttpContextAccessor](/dotnet/api/microsoft.aspnetcore.http.ihttpcontextaccessor) interface and its default implementation [HttpContextAccessor](/dotnet/api/microsoft.aspnetcore.http.httpcontextaccessor). It's only necessary to use `IHttpContextAccessor` when you need access to the `HttpContext` inside a service.

::: moniker range=">= aspnetcore-2.0"

## Use HttpContext from Razor Pages

The Razor Pages [PageModel](/dotnet/api/microsoft.aspnetcore.mvc.razorpages.pagemodel) exposes the [HttpContext](/dotnet/api/microsoft.aspnetcore.mvc.razorpages.pagemodel.httpcontext) property:

```csharp
public class AboutModel : PageModel
{
    public string Message { get; set; }

    public void OnGet()
    {
        Message = HttpContext.Request.PathBase;
    }
}
```

::: moniker-end

## Use HttpContext from a Razor view

Razor views expose the `HttpContext` directly via a [RazorPage.Context](/dotnet/api/microsoft.aspnetcore.mvc.razor.razorpage.context#Microsoft_AspNetCore_Mvc_Razor_RazorPage_Context) property on the view. The following example retrieves the current username in an Intranet app using Windows Authentication:

```cshtml
@{
    var username = Context.User.Identity.Name;
}
```

## Use HttpContext from a controller

Controllers expose the [ControllerBase.HttpContext](/dotnet/api/microsoft.aspnetcore.mvc.controllerbase.httpcontext) property:

```csharp
public class HomeController : Controller
{
    public IActionResult About()
    {
        var pathBase = HttpContext.Request.PathBase;
        // Do something with the PathBase.

        return View();
    }
}
```

## Use HttpContext from middleware

When working with custom middleware components, `HttpContext` is passed into the `Invoke` or `InvokeAsync` method and can be accessed when the middleware is configured:

```csharp
public class MyCustomMiddleware
{
    public Task InvokeAsync(HttpContext context)
    {
        // Middleware initialization optionally using HttpContext
    }
}
```

## Use HttpContext from custom components

For other framework and custom components that require access to `HttpContext`, the recommended approach is to register a dependency using the built-in [dependency injection](xref:fundamentals/dependency-injection) container. The dependency injection container supplies the `IHttpContextAccessor` to any classes that declare it as a dependency in their constructors.

::: moniker range=">= aspnetcore-2.1"

```csharp
public void ConfigureServices(IServiceCollection services)
{
     services.AddMvc()
         .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
     services.AddHttpContextAccessor();
     services.AddTransient<IUserRepository, UserRepository>();
}
```

::: moniker-end

::: moniker range="<= aspnetcore-2.0"

```csharp
public void ConfigureServices(IServiceCollection services)
{
     services.AddMvc();
     services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
     services.AddTransient<IUserRepository, UserRepository>();
}
```

::: moniker-end

In the following example:

* `UserRepository` declares its dependency on `IHttpContextAccessor`.
* The dependency is supplied when dependency injection resolves the dependency chain and creates an instance of `UserRepository`.

```csharp
public class UserRepository : IUserRepository
{
    private readonly IHttpContextAccessor _httpContextAccessor;

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

    public void LogCurrentUser()
    {
        var username = _httpContextAccessor.HttpContext.User.Identity.Name;
        service.LogAccessRequest(username);
    }
}
```

## HttpContext access from a background thread

`HttpContext` is not thread-safe. Reading or writing properties of the `HttpContext` outside of processing a request can result in a `NullReferenceException`.

> [!NOTE]
> Using `HttpContext` outside of processing a request often results in a `NullReferenceException`. If your app generates sporadic `NullReferenceException`s , review parts of the code that start background processing, or that continue processing after a request completes. Look for a mistakes like defining a controller method as `async void`.

To safely perform background work with `HttpContext` data:

* Copy the required data during request processing.
* Pass the copied data to a background task.

To avoid unsafe code, never pass the `HttpContext` into a method that does background work - pass the data you need instead.

```csharp
public class EmailController
{
    public ActionResult SendEmail(string email)
    {
        var correlationId = HttpContext.Request.Headers["x-correlation-id"].ToString();

        // Starts sending an email, but doesn't wait for it to complete
        _ = SendEmailCore(correlationId);
        return View();
    }

    private async Task SendEmailCore(string correlationId)
    {
        // send the email
    }
}