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HttpWebRequest.PreAuthenticate Property

Gets or sets a value that indicates whether to send an Authorization header with the request.

Namespace:  System.Net
Assembly:  System (in System.dll)

abstract PreAuthenticate : bool with get, set 
override PreAuthenticate : bool with get, set

Property Value

Type: System.Boolean
true to send an HTTP Authorization header with requests after authentication has taken place; otherwise, false. The default is false.

After a client request to a specific Uri is successfully authenticated, if 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 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.

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

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.

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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