WebRequest.RegisterPrefix Method (String, IWebRequestCreate)


The .NET API Reference documentation has a new home. Visit the .NET API Browser on docs.microsoft.com to see the new experience.

Registers a WebRequest descendant for the specified URI.

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

Public Shared Function RegisterPrefix (
	prefix As String,
	creator As IWebRequestCreate
) As Boolean


Type: System.String

The complete URI or URI prefix that the WebRequest descendant services.

Type: System.Net.IWebRequestCreate

The create method that the WebRequest calls to create the WebRequest descendant.

Return Value

Type: System.Boolean

true if registration is successful; otherwise, false.

Exception Condition

prefix is null


creator is null.

The RegisterPrefix method registers WebRequest descendants to service requests. WebRequest descendants are typically registered to handle a specific protocol, such HTTP or FTP, but can be registered to handle a request to a specific server or path on a server.

The pre-registered reserve types already registered include the following:

  • http://

  • https://

  • ftp://

  • file://

For more information, see the Create(String) and Create(Uri) methods.

Duplicate prefixes are not allowed. RegisterPrefix returns false if an attempt is made to register a duplicate prefix.


The HttpWebRequest class is registered to service requests for HTTP and HTTPS schemes by default. Attempts to register a different WebRequest descendant for these schemes will fail.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Return to top