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WebHeaderCollection.IsRestricted Method (String, Boolean)

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

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

Public Shared Function IsRestricted ( _
	headerName As String, _
	response As Boolean _
) As Boolean
Dim headerName As String
Dim response As Boolean
Dim returnValue As Boolean

returnValue = WebHeaderCollection.IsRestricted(headerName, response)
public static boolean IsRestricted (
	String headerName, 
	boolean response
public static function IsRestricted (
	headerName : String, 
	response : boolean
) : boolean
Not applicable.



The header to test.


Does the Framework test the response or the request?

Return Value

true if the header is restricted; otherwise, false.

Exception typeCondition


headerName is a null reference (Nothing in Visual Basic) or Empty.


headerName contains invalid characters.

The IsRestricted method returns true to indicate that a request or response 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 request headers are prohibited from being set.

Public Shared Sub Main()
        'Create a web request for "".
        Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create(""), 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))
                Console.WriteLine("'{0}' is not a restricted header", myWebHeaderCollection.AllKeys(i))
            End If 
    Catch e As WebException
        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
    End Try
End Sub 'Main

    try {
        // Create a web request for "".
        HttpWebRequest myHttpWebRequest = (HttpWebRequest)(WebRequest.
        // Get the associated response for the above request.
        HttpWebResponse myHttpWebResponse = (HttpWebResponse)(
        // Get the headers associated with the response.
        WebHeaderCollection myWebHeaderCollection =

        for (int i = 0; i < myWebHeaderCollection.get_Count(); i++) {
            // Check if the first response header is restriced.
            if (WebHeaderCollection.IsRestricted(myWebHeaderCollection.
                get_AllKeys()[i])) {
                Console.WriteLine("'{0}' is a restricted header",
            else {
                Console.WriteLine("'{0}' is not a restricted header",
    catch (WebException e) {
        Console.WriteLine("\nWebException is thrown.\nMessage is:" 
            + e.get_Message());
        if (e.get_Status().Equals(WebExceptionStatus.ProtocolError)) {
            Console.WriteLine("Status Code : {0}", ((HttpWebResponse)(
            Console.WriteLine("Status Description : {0}", ((
            Console.WriteLine("Server : {0}", ((HttpWebResponse)(
    catch (System.Exception e) {
        Console.WriteLine("Exception is thrown. Message is :" 
            + e.get_Message());
} //main

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0