System.Net.Http Namespace

.NET Framework 4.5

The System.Net.Http namespace provides a programming interface for modern HTTP applications.

The System.Net.Http namespace is designed to provide the following:

  1. HTTP client components that allow users to consume modern web services over HTTP.

  2. HTTP components that can be used by both clients and servers (HTTP headers and messages, for example). This provides a consistent programming model on both the client and the server side for modern web services over HTTP.

The System.Net.Http namespace and the related System.Net.Http.Headers namespace provide the following set of components:

  1. HttpClient - the primary class used to send and receive requests over HTTP.

  2. HttpRequestMessage and HttpResponseMessage - HTTP messages as defined in RFC 2616 by the IETF.

  3. HttpHeaders - HTTP headers as defined in RFC 2616 by the IETF.

  4. HttpClientHandler - HTTP handlers responsible for producing HTTP response messages.

There are various HTTP message handles that can be used. These include the following.

  1. DelegatingHandler - A class used to plug a handler into a handler chain.

  2. HttpMessageHandler - A simple to class to derive from that supports the most common requirements for most applications.

  3. HttpClientHandler - A class that operates at the bottom of the handler chain that actually handles the HTTP transport operations.

  4. WebRequestHandler - A specialty class that operates at the bottom of the handler chain class that handles HTTP transport operations with options that are specific to the System.Net.HttpWebRequest object.

The contents of an HTTP message corresponds to the entity body defined in RFC 2616.

A number of classes can be used for HTTP content. These include the following.

  1. ByteArrayContent - HTTP content based on a byte array.

  2. FormUrlEncodedContent - HTTP content of name/value tuples encoded using application/x-www-form-urlencoded MIME type.

  3. MultipartContent - HTTP content that gets serialized using the multipart/* content type specification.

  4. MultipartFormDataContent - HTTP content encoded using the multipart/form-data MIME type.

  5. StreamContent - HTTP content based on a stream.

  6. StringContent - HTTP content based on a string.

If an app using the System.Net.Http and System.Net.Http.Headers namespaces intends to download large amounts of data (50 megabytes or more), then the app should stream those downloads and not use the default buffering. If the default buffering is used the client memory usage will get very large, potentially resulting in substantially reduced performance.

Classes in the System.Net.Http and System.Net.Http.Headers namespaces can be used to develop Windows Store apps or desktop apps. When used in a Windows Store app, classes in the System.Net.Http and System.Net.Http.Headers namespaces are affected by network isolation feature, part of the application security model used by the Windows 8. The appropriate network capabilities must be enabled in the app manifest for a Windows Store app for the system to allow network access by a Windows store app. For more information, see the Network Isolation for Windows Store Apps.

  Class Description
Public class ByteArrayContent Provides HTTP content based on a byte array.
Public class DelegatingHandler A type for HTTP handlers that delegate the processing of HTTP response messages to another handler, called the inner handler.
Public class FormUrlEncodedContent A container for name/value tuples encoded using application/x-www-form-urlencoded MIME type.
Public class HttpClient Provides a base class for sending HTTP requests and receiving HTTP responses from a resource identified by a URI.
Public class HttpClientHandler The default message handler used by HttpClient.
Public class HttpContent A base class representing an HTTP entity body and content headers.
Public class HttpMessageHandler A base type for HTTP message handlers.
Public class HttpMessageInvoker A specialty class that allows applications to call the SendAsync method on an Http handler chain.
Public class HttpMethod A helper class for retrieving and comparing standard HTTP methods and for creating new HTTP methods.
Public class HttpRequestException A base class for exceptions thrown by the HttpClient and HttpMessageHandler classes.
Public class HttpRequestMessage Represents a HTTP request message.
Public class HttpResponseMessage Represents a HTTP response message including the status code and data.
Public class MessageProcessingHandler A base type for handlers which only do some small processing of request and/or response messages.
Public class MultipartContent Provides a collection of HttpContent objects that get serialized using the multipart/* content type specification.
Public class MultipartFormDataContent Provides a container for content encoded using multipart/form-data MIME type.
Public class RtcRequestFactory Represents the class that is used to create special HttpRequestMessage for use with the Real-Time-Communications (RTC) background notification infrastructure.
Public class StreamContent Provides HTTP content based on a stream.
Public class StringContent Provides HTTP content based on a string.
Public class WebRequestHandler Provides desktop-specific features not available to Windows Store apps or other environments.

  Enumeration Description
Public enumeration ClientCertificateOption Specifies how client certificates are provided.
Public enumeration HttpCompletionOption Indicates if HttpClient operations should be considered completed either as soon as a response is available, or after reading the entire response message including the content.
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