This documentation is archived and is not being maintained.

WebHeaderCollection.IsRestricted Method (String)

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

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

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

returnValue = WebHeaderCollection.IsRestricted(headerName)


Type: System.String

The header to test.

Return Value

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


headerName is Nothing or Empty.


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()
            '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 S"".
      HttpWebRequest* myHttpWebRequest =
         dynamic_cast<HttpWebRequest*> (WebRequest::Create(S""));

      // Get the associated response for the above request.
      HttpWebResponse* myHttpWebResponse =
         dynamic_cast<HttpWebResponse*> (myHttpWebRequest->GetResponse());

      // Get the headers associated with the response.
      WebHeaderCollection* myWebHeaderCollection = myHttpWebResponse->Headers;

      for (int i = 0; i < myWebHeaderCollection->Count;i++) {
         // Check if the first response header is restriced.
         if (WebHeaderCollection::IsRestricted(dynamic_cast<String __gc *>(myWebHeaderCollection->AllKeys->Item[i])))
            Console::WriteLine(S"' {0}' is a restricted header",
            Console::WriteLine(S"' {0}' is not a restricted header",
   } catch (WebException* e) {
      Console::WriteLine(S"\nWebException is thrown.\nMessage is: {0}", e->Message);
      if (e->Status == WebExceptionStatus::ProtocolError) {
         Console::WriteLine(S"Status Code : {0}", __box((dynamic_cast<HttpWebResponse*>(e->Response))->StatusCode));
         Console::WriteLine(S"Status Description : {0}", (dynamic_cast<HttpWebResponse*>(e->Response))->StatusDescription);
         Console::WriteLine(S"Server : {0}", (dynamic_cast<HttpWebResponse*>(e->Response))->Server);
   } catch (Exception* e) {
      Console::WriteLine(S"Exception is thrown. Message is : {0}", e->Message);

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0