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WebHeaderCollection.Add Method (String)

Inserts the specified header into the collection.

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

'Declaration
Public Sub Add ( _
	header As String _
)

Parameters

header
Type: System.String

The header to add, with the name and value separated by a colon.

ExceptionCondition
ArgumentNullException

header is Nothing or Empty.

ArgumentException

header does not contain a colon (:) character.

The length of value is greater than 65535.

-or-

The name part of header is Empty or contains invalid characters.

-or-

header is a restricted header that should be set with a property.

-or-

The value part of header contains invalid characters.

ArgumentOutOfRangeException

The length the string after the colon (:) is greater than 65535.

The header parameter must be specified in the format "name:value". If the specified header does not exist in the collection, a new header is added to the collection.

If the header specified in header is already present in the collection, the value part of the header is concatenated with the existing value.

The following example adds a name/value pair to a WebHeaderCollection using the Add Method.

    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 headers associated with the request. 
            Dim myWebHeaderCollection As WebHeaderCollection = myHttpWebRequest.Headers

   	    Console.WriteLine("Configuring Webrequest to accept Danish and English language using 'Add' method")

	    'Add the Accept-Language header (for Danish) in the request.
            myWebHeaderCollection.Add("Accept-Language:da")

            'Include English in the Accept-Langauge header. 
            myWebHeaderCollection.Add("Accept-Language","en;q" + ChrW(61) + "0.8")

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

            'Print the headers for the request.
            printHeaders(myWebHeaderCollection)
            myHttpWebResponse.Close()
        'Catch exception if trying to add a restricted header. 
        Catch e As ArgumentException
            Console.WriteLine(e.Message)
        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: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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.

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