The AddHeader function adds a header to the current SIP message.
bool AddHeader( string or StandardHeader value name, string value );
Returns true if the header was successfully added; false if it was not. If the header already exists, this function returns false.
If you add a header with this method and call Respond, the new header will not be included in the response. All new headers that should be in the response must be added as additional parameters to Respond.
AddHeader can be used to pass contextual information from an MSPL script to a managed application, through the use of a custom header.
In a managed application, these custom headers can be retrieved by calling Message.GetHeaders, which returns a HeaderCollection. This collection can be searched for the specific custom header added with AddHeader.