/// <summary>
/// Gets the $callback query parameter if present. Also performs some validation:
/// We do not allow $callback to be present if the content-type for the response is going to be anythign but JSON or plain text.
/// </summary>
/// <param name="message">The request message.</param>
/// <param name="format">The format we will write the reponse in.</param>
/// <returns>Returns the name of the callback function $callback specifies, or null if there isn't one.</returns>
internal static string HandleCallbackQueryOption(AstoriaRequestMessage message, ODataFormatWithParameters format)
{
var functionName = message.GetQueryStringItem(XmlConstants.HttpQueryStringCallback);
if (functionName != null)
{
// The verb must be GET (not IsQuery(), GET specifically)
if (message.HttpVerb != HttpVerbs.GET)
{
throw new DataServiceException(400, Strings.CallbackQueryOptionHandler_GetRequestsOnly);
}
// If conneg didn't get a format, that means that there was some error that we will fail at later, or
// it is going end up being a 204, 304, or something else with no body. For all of these cases we are OK
// with 'pretending' that $callback was not there, since the other errors are probably more important than
// ours, and in the non-error cases we really should not be throwing (think 204).
if (format == null)
{
return(null);
}
// JSON and text/plain are the only things allowed with $callback
if (format.Format != ODataFormat.Json && format.Format != ODataFormat.RawValue)
{
throw new DataServiceException(400, Strings.CallbackQueryOptionHandler_UnsupportedContentType(format.Format.ToString()));
}
}
return(functionName);
}
