Specifies a collection of the name/value pairs that make up the HTTP headers.
Assemblies: System (in System.dll)
System.Net.Requests (in System.Net.Requests.dll)
The collection contains the protocol headers associated with the request. The following table lists the HTTP headers that are not stored in the collection but are either set by the system or set by properties or methods.
Set by the Accept property.
Set by the ContentLength property.
Set by the ContentType property.
Set by the Expect property.
Set by the Date property.
Set by the Host property.
Set by the IfModifiedSince property.
Set by the AddRange method.
Set by the Referer property.
Set by the UserAgent property.
You should not assume that the header values will remain unchanged, because Web servers and caches may change or add headers to a Web request.
.NET FrameworkSupported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0
.NET Framework Client ProfileSupported in: 4, 3.5 SP1
Portable Class LibrarySupported in: Portable Class Library
.NET for Windows Store appsSupported in: Windows 8
Supported in: Windows Phone 8.1
Supported in: Windows Phone Silverlight 8.1
Supported in: Windows Phone Silverlight 8
Windows Phone 8.1, Windows Phone 8, 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.