HttpWebRequest Class

Definition

Namespace:

System.Net

Assembly:

System.Net.Requests.dll

Source:

HttpWebRequest.cs

Provides an HTTP-specific implementation of the WebRequest class.

public ref class HttpWebRequest : System::Net::WebRequest, System::Runtime::Serialization::ISerializable

public class HttpWebRequest : System.Net.WebRequest, System.Runtime.Serialization.ISerializable

type HttpWebRequest = class
    inherit WebRequest
    interface ISerializable

Public Class HttpWebRequest
Inherits WebRequest
Implements ISerializable

Inheritance

Object

MarshalByRefObject

WebRequest

HttpWebRequest

Implements

ISerializable

Examples

The following code example creates an HttpWebRequest for the URI http://www.contoso.com/.

HttpWebRequest^ myReq = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "http://www.contoso.com/" ));

HttpWebRequest myReq =
(HttpWebRequest)WebRequest.Create("http://www.contoso.com/");

Dim myReq As HttpWebRequest = _
    WebRequest.Create("http://www.contoso.com/")

Remarks

Caution

WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete, and you shouldn't use them for new development. Use HttpClient instead.

The HttpWebRequest class provides support for the properties and methods defined in WebRequest and for additional properties and methods that enable the user to interact directly with servers using HTTP.

Do not use the HttpWebRequest constructor. Use the WebRequest.Create method to initialize new HttpWebRequest objects. If the scheme for the Uniform Resource Identifier (URI) is http:// or https://, Create returns an HttpWebRequest object.

The GetResponse method makes a synchronous request to the resource specified in the RequestUri property and returns an HttpWebResponse that contains the response object. The response data can be received by using the stream returned by GetResponseStream. If the response object or the response stream is closed, remaining data will be forfeited. The remaining data will be drained and the socket will be re-used for subsequent requests when closing the response object or stream if the following conditions hold: it's a keep-alive or pipelined request, only a small amount of data needs to be received, or the remaining data is received in a small time interval. If none of the mentioned conditions hold or the drain time is exceeded, the socket will be closed. For keep-alive or pipelined connections, we strongly recommend that the application reads the streams until EOF. This ensures that the socket will be re-used for subsequent requests resulting in better performance and less resources used.

When you want to send data to the resource, the GetRequestStream method returns a Stream object to use to send data. The BeginGetRequestStream and EndGetRequestStream methods provide asynchronous access to the send data stream.

For client authentication with HttpWebRequest, the client certificate must be installed in the My certificate store of the current user.

The HttpWebRequest class throws a WebException when errors occur while accessing a resource. The WebException.Status property contains a WebExceptionStatus value that indicates the source of the error. When WebException.Status is WebExceptionStatus.ProtocolError, the Response property contains the HttpWebResponse received from the resource.

HttpWebRequest exposes common HTTP header values sent to the Internet resource as properties, set by methods, or set by the system; the following table contains a complete list. You can set other headers in the Headers property as name/value pairs. Note that servers and caches may change or add headers during the request.

The following table lists the HTTP headers that are set either by properties or methods or the system.

Header	Set by
Accept	Set by the Accept property.
Connection	Set by the Connection property, KeepAlive property.
Content-Length	Set by the ContentLength property.
Content-Type	Set by the ContentType property.
Expect	Set by the Expect property.
Date	Set by the system to current date.
Host	Set by the system to current host information.
If-Modified-Since	Set by the IfModifiedSince property.
Range	Set by the AddRange method.
Referer	Set by the Referer property.
Transfer-Encoding	Set by the TransferEncoding property (the SendChunked property must be true).
User-Agent	Set by the UserAgent property.

Note

HttpWebRequest is registered automatically. You do not need to call the RegisterPrefix method to register System.Net.HttpWebRequest before using URIs beginning with http:// or https://.

The local computer or application config file may specify that a default proxy be used. If the Proxy property is specified, then the proxy settings from the Proxy property override the local computer or application config file and the HttpWebRequest instance will use the proxy settings specified. If no proxy is specified in a config file and the Proxy property is unspecified, the HttpWebRequest class uses the proxy settings inherited from Internet options on the local computer. If there are no proxy settings in Internet options, the request is sent directly to the server.

Note

The Framework caches SSL sessions as they are created and attempts to reuse a cached session for a new request, if possible. When attempting to reuse an SSL session, the Framework uses the first element of ClientCertificates (if there is one), or tries to reuse an anonymous sessions if ClientCertificates is empty.

Note

For security reasons, cookies are disabled by default. If you want to use cookies, use the CookieContainer property to enable cookies.

The .NET Framework 4.6 includes a new security feature that blocks insecure cipher and hashing algorithms for connections. Applications using TLS/SSL through APIs such as HttpClient, HttpWebRequest, FTPClient, SmtpClient, SslStream, etc. and targeting .NET Framework 4.6 get the more-secure behavior by default.

Developers may want to opt out of this behavior in order to maintain interoperability with their existing SSL3 services OR TLS w/ RC4 services. This article explains how to modify your code so that the new behavior is disabled.

Constructors

HttpWebRequest(SerializationInfo, StreamingContext)

Obsolete. Initializes a new instance of the HttpWebRequest class from the specified instances of the SerializationInfo and StreamingContext classes. This constructor is obsolete.

Properties

Accept	Gets or sets the value of the Accept HTTP header.
Address	Gets the Uniform Resource Identifier (URI) of the Internet resource that actually responds to the request.
AllowAutoRedirect	Gets or sets a value that indicates whether the request should follow redirection responses.
AllowReadStreamBuffering	Gets or sets a value that indicates whether to buffer the received from the Internet resource.
AllowWriteStreamBuffering	Gets or sets a value that indicates whether to buffer the data sent to the Internet resource.
AuthenticationLevel	Gets or sets values indicating the level of authentication and impersonation used for this request. (Inherited from WebRequest)
AutomaticDecompression	Gets or sets the type of decompression that is used.
CachePolicy	Gets or sets the cache policy for this request. (Inherited from WebRequest)
ClientCertificates	Gets or sets the collection of security certificates that are associated with this request.
Connection	Gets or sets the value of the Connection HTTP header.
ConnectionGroupName	Gets or sets the name of the connection group for the request.
ContentLength	Gets or sets the Content-length HTTP header.
ContentType	Gets or sets the value of the Content-type HTTP header.
ContinueDelegate	Gets or sets the delegate method called when an HTTP 100-continue response is received from the Internet resource.
ContinueTimeout	Gets or sets a timeout, in milliseconds, to wait until the 100-Continue is received from the server.
CookieContainer	Gets or sets the cookies associated with the request.
CreatorInstance	When overridden in a descendant class, gets the factory object derived from the IWebRequestCreate class used to create the WebRequest instantiated for making the request to the specified URI. (Inherited from WebRequest)
Credentials	Gets or sets authentication information for the request.
Date	Gets or sets the Date HTTP header value to use in an HTTP request.
DefaultCachePolicy	Gets or sets the default cache policy for this request.
DefaultMaximumErrorResponseLength	Gets or sets the default maximum length of an HTTP error response.
DefaultMaximumResponseHeadersLength	Gets or sets the default for the MaximumResponseHeadersLength property.
Expect	Gets or sets the value of the Expect HTTP header.
HaveResponse	Gets a value that indicates whether a response has been received from an Internet resource.
Headers	Specifies a collection of the name/value pairs that make up the HTTP headers.
Host	Gets or sets the Host header value to use in an HTTP request independent from the request URI.
IfModifiedSince	Gets or sets the value of the If-Modified-Since HTTP header.
ImpersonationLevel	Gets or sets the impersonation level for the current request. (Inherited from WebRequest)
KeepAlive	Gets or sets a value that indicates whether to make a persistent connection to the Internet resource.
MaximumAutomaticRedirections	Gets or sets the maximum number of redirects that the request follows.
MaximumResponseHeadersLength	Gets or sets the maximum allowed length of the response headers.
MediaType	Gets or sets the media type of the request.
Method	Gets or sets the method for the request.
Pipelined	Gets or sets a value that indicates whether to pipeline the request to the Internet resource.
PreAuthenticate	Gets or sets a value that indicates whether to send an Authorization header with the request.
ProtocolVersion	Gets or sets the version of HTTP to use for the request.
Proxy	Gets or sets proxy information for the request.
ReadWriteTimeout	Gets or sets a time-out in milliseconds when writing to or reading from a stream.
Referer	Gets or sets the value of the Referer HTTP header.
RequestUri	Gets the original Uniform Resource Identifier (URI) of the request.
SendChunked	Gets or sets a value that indicates whether to send data in segments to the Internet resource.
ServerCertificateValidationCallback	Gets or sets a callback function to validate the server certificate.
ServicePoint	Gets the service point to use for the request.
SupportsCookieContainer	Gets a value that indicates whether the request provides support for a CookieContainer.
Timeout	Gets or sets the time-out value in milliseconds for the GetResponse() and GetRequestStream() methods.
TransferEncoding	Gets or sets the value of the Transfer-encoding HTTP header.
UnsafeAuthenticatedConnectionSharing	Gets or sets a value that indicates whether to allow high-speed NTLM-authenticated connection sharing.
UseDefaultCredentials	Gets or sets a Boolean value that controls whether default credentials are sent with requests.
UserAgent	Gets or sets the value of the User-agent HTTP header.

Methods

Abort()	Cancels a request to an Internet resource.
AddRange(Int32, Int32)	Adds a byte range header to the request for a specified range.
AddRange(Int32)	Adds a byte range header to a request for a specific range from the beginning or end of the requested data.
AddRange(Int64, Int64)	Adds a byte range header to the request for a specified range.
AddRange(Int64)	Adds a byte range header to a request for a specific range from the beginning or end of the requested data.
AddRange(String, Int32, Int32)	Adds a range header to a request for a specified range.
AddRange(String, Int32)	Adds a Range header to a request for a specific range from the beginning or end of the requested data.
AddRange(String, Int64, Int64)	Adds a range header to a request for a specified range.
AddRange(String, Int64)	Adds a Range header to a request for a specific range from the beginning or end of the requested data.
BeginGetRequestStream(AsyncCallback, Object)	Begins an asynchronous request for a Stream object to use to write data.
BeginGetResponse(AsyncCallback, Object)	Begins an asynchronous request to an Internet resource.
CreateObjRef(Type)	Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject)
EndGetRequestStream(IAsyncResult, TransportContext)	Ends an asynchronous request for a Stream object to use to write data and outputs the TransportContext associated with the stream.
EndGetRequestStream(IAsyncResult)	Ends an asynchronous request for a Stream object to use to write data.
EndGetResponse(IAsyncResult)	Ends an asynchronous request to an Internet resource.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetLifetimeService()	Obsolete. Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject)
GetObjectData(SerializationInfo, StreamingContext)	Obsolete. Populates a SerializationInfo with the data required to serialize the target object.
GetRequestStream()	Gets a Stream object to use to write request data.
GetRequestStream(TransportContext)	Gets a Stream object to use to write request data and outputs the TransportContext associated with the stream.
GetRequestStreamAsync()	When overridden in a descendant class, returns a Stream for writing data to the Internet resource as an asynchronous operation. (Inherited from WebRequest)
GetResponse()	Returns a response from an Internet resource.
GetResponseAsync()	When overridden in a descendant class, returns a response to an Internet request as an asynchronous operation. (Inherited from WebRequest)
GetType()	Gets the Type of the current instance. (Inherited from Object)
InitializeLifetimeService()	Obsolete. Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
MemberwiseClone(Boolean)	Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject)
ToString()	Returns a string that represents the current object. (Inherited from Object)

Explicit Interface Implementations

ISerializable.GetObjectData(SerializationInfo, StreamingContext)

Obsolete. Populates a SerializationInfo with the data needed to serialize the target object.

See also

• DefaultProxy Element (Network Settings)
• Changes to NTLM authentication for HTTPWebRequest in Version 3.5 SP1