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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 _
)
'Usage
Dim instance As WebHeaderCollection
Dim header As String

instance.Add(header)
public void Add (
	String header
)
public function Add (
	header : String
)
Not applicable.

Parameters

header

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

Exception typeCondition

ArgumentNullException

header is a null reference (Nothing in Visual Basic) 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

try {
    //Create a web request for "www.msn.com".
    HttpWebRequest myHttpWebRequest = (HttpWebRequest)(
        WebRequest.Create("http://www.msn.com"));
    //Get the headers associated with the request.
    WebHeaderCollection myWebHeaderCollection = myHttpWebRequest.
        get_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=0.8");
    //Get the associated response for the above request.
    HttpWebResponse myHttpWebResponse = (HttpWebResponse)
        myHttpWebRequest.GetResponse();
    //Print the headers for the request.
    PrintHeaders(myWebHeaderCollection);
    myHttpWebResponse.Close();
}
//Catch exception if trying to add a restricted header.

catch (ArgumentException e) {
    Console.WriteLine(e.get_Message());
}
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)(
            e.get_Response())).get_StatusCode());
        Console.WriteLine("Status Description : {0}", ((HttpWebResponse)(
            e.get_Response())).get_StatusDescription());
        Console.WriteLine("Server : {0}", ((HttpWebResponse)(
            e.get_Response())).get_Server());
    }
}
catch (System.Exception e) {
    Console.WriteLine("Exception is thrown. Message is :" 
        + e.get_Message());
}

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, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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