403 words (approximately 2 mins)

Overview [ Documentation]

HttpContext encapsulates all information about an HTTP request and response.

  • Initialized when HTTP request is received
  • Accessible by middleware and app frameworks

HttpContext is not thread safe.

HttpRequest

Accessed via HttpContext.Request.

  • Initialized when HTTP request is received
  • Mutable

Common members:

  • Path, Method, Headers
  • RouteValues — a collection of route values; set when request is matched to a route
  • Query — a collection of query values parsed from QueryString
  • ReadFormAsync() — reads request body as a form and returns a form values collection
  • Body — a Stream for reading the request body

HttpRequest.Headers

Access headers in this collection by either:

  • Providing header name to indexer: request.Headers["x-some-custom-header"]
  • Using its properties: request.Headers.UserAgent

HttpRequest.Body

Allows request body to be read with Stream:

context.Request.Body.CopyToAsync(writeStream);

A request body can only be read once. To read multiple times, use the EnableBuffering extension method:

context.Request.EnableBuffering() // must be called before reading request body
await ReadRequestBody(context.Request.Body); // read the body
context.Request.Body.Position = 0; // rewind the request body

HttpResponse

Accessed via HttpContext.Response. Used to set information on the HTTP response sent back to the client.

Common members:

  • StatusCode, ContentType, Headers (all of these must be set before writing to the response body)
  • Body — a Stream for writing the response body

Responses are started by flushing response body or calling HttpResponse.StartAsync. Use HttpResponse.HasStarted to check for start.

HttpResponse.Headers

Access headers in this collection by either:

  • Providing header name to indexer: response.Headers.CacheControl = “no-cache”;
  • Using its properties: response.Headers[“x-some-custom-header”] = “custom value”;

HttpResponse.Body

Allows response body to be written with Stream:

await using var fileStream = File.OpenRead(filePath);
await fileStream.CopyToAsync(context.Response.Body);

Response Trailers

HTTP/2 and HTTP/3 support response trailers — headers sent with the response after the body is complete. To set trailers, use AppendTrailer:

if (response.SupportsTrailers())
    response.AppendTrailer("trailername", "TrailerValue");

HttpContext.RequestAborted

A cancellation token. Pass to long-running tasks so that they can cancel if a request is aborted (like a database query).
Do not use on request body read or write operations.

HttpContext.Abort()

Triggers HttpContext.RequestAborted cancellation token and send notification to client.
Does not trigger an HTTP response 400 (error).

HttpContext.User

Gets or sets the user, represented by ClaimsPrincipal, for the request.

HttpContext.Features

A collection of feature interfaces for the current request.
Mutable even within the context of a request (so middleware can change it).

var feature = httpContext.Features.Get<IHttpMinRequestBodyDataRateFeature>(); // Get a feature from the collection
if (feature != null)
    feature.MinDataRate = null; // Set MinDataRate to null