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WebHeaderCollection.IsRestricted Method (String)

Tests whether the specified HTTP header can be set for the request.

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

'Declaration
Public Shared Function IsRestricted ( _
	headerName As String _
) As Boolean

Parameters

headerName
Type: System.String
The header to test.

Return Value

Type: System.Boolean
true if the header is restricted; otherwise false.

ExceptionCondition
ArgumentNullException

headerName is Nothing or Empty.

ArgumentException

headerName contains invalid characters.

The IsRestricted method returns true to indicate that a header is restricted and must be set using properties instead of directly or is set by the system. The restricted headers are:

  • Accept

  • Connection

  • Content-Length

  • Content-Type

  • Date

  • Expect

  • Host

  • If-Modified-Since

  • Range

  • Referer

  • Transfer-Encoding

  • User-Agent

  • Proxy-Connection

The following example checks the IsRestricted property to see if any headers are prohibited from being set.


    Public Shared Sub Main()
	Try
            'Create a web request for "www.msn.com".
            Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create("http://www.msn.com"), HttpWebRequest)

            'Get the associated response for the above request.
            Dim myHttpWebResponse As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)

            'Get the headers associated with the response.
            Dim myWebHeaderCollection As WebHeaderCollection = myHttpWebResponse.Headers

            'Check if the first response header is restricted.
	    dim i as integer
	    for i =0 to myWebHeaderCollection.Count-1
	            If WebHeaderCollection.IsRestricted(myWebHeaderCollection.AllKeys(i)) Then
	                Console.WriteLine("'{0}' is a restricted header", myWebHeaderCollection.AllKeys(i))
	            Else
	                Console.WriteLine("'{0}' is not a restricted header", myWebHeaderCollection.AllKeys(i))
	            End If 
	    next
        myHttpWebResponse.Close()
        Catch e As WebException
            Console.WriteLine(e.Message)
            If e.Status = WebExceptionStatus.ProtocolError Then
                Console.WriteLine("Status Code : {0}", CType(e.Response, HttpWebResponse).StatusCode)
                Console.WriteLine("Status Description : {0}", CType(e.Response, HttpWebResponse).StatusDescription)
                Console.WriteLine("Server : {0}", CType(e.Response, HttpWebResponse).Server)
            End If
        Catch e As Exception
            Console.WriteLine(e.Message)
        End Try
    End Sub 'Main


.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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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