Gets or sets a value that indicates whether to send an Authorization header with the request.
Syntax
Value
true to send a HTTP WWW-authenticate header with the current instance without waiting for an authentication challenge from the requested resource; otherwise, false. The default is false.
Remarks
After a client request to a specific Uri is successfully authenticated, if HttpWebRequest.PreAuthenticate is true and credentials are supplied, the Authorization header is sent with each request to any Uri that matches the specific Uri up to the last forward slash. So if the client request successfully authenticated to a specific Uri that contains the following:
http://www.contoso.com/firstpath/
Then the Authorization header for preauthentication is sent with each request to any of the following Uri instances:
http://www.contoso.com/firstpath/
http://www.contoso.com/firstpath/default
http://www.contoso.com/firstpath/default.html
http://www.contoso.com/firstpath/sample.html
However, the Authorization header is not sent with requests to any of the following Uri instances:
http://www.contoso.com/
http://www.contoso.com/firstpath
http://www.contoso.com/secondpath/
If the client request to a specific Uri is not successfully authenticated, the request uses standard authentication procedures.
With the exception of the first request, the WebRequest.PreAuthenticate property indicates whether to send authentication information with subsequent requests to a Uri that matches the specific Uri up to the last forward slash without waiting to be challenged by the server.
The following dialog between client and server illustrates the effect of this property. The dialog assumes that basic authentication is in use.
HttpWebRequest.PreAuthenticate is false:
Client: GET someUrl
Server: 401 WWW-Authenticate Basic
Client: GET with Authorization headers
Server: 200 OK
Client: GET someUrl
Server: 401 WWW-Authenticate Basic
Client: GET with Authorization headers
Server: 200 OK
HttpWebRequest.PreAuthenticate is true:
Client: GET someUrl
Server: 401 WWW-Authenticate Basic
Client: GET with Authorization headers
Server: 200 OK
Client: GET someUrl with Authorization headers
If the authentication scheme does not support preauthentication, the value of this property is ignored.
Requirements
Assembly: System (in System.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0