/// <summary>
/// Creates the 'feature' XML element which is part of a 'Stream Initiation'
/// request.
/// </summary>
/// <param name="streamOptions">An enumerable collection of accepted stream
/// methods.</param>
/// <returns>An XML 'feature' element.</returns>
/// <exception cref="ArgumentNullException">The streamOptions parameter
/// is null.</exception>
private XElement CreateFeatureElement(IEnumerable <string> streamOptions)
{
streamOptions.ThrowIfNull("streamOptions");
// Create the data-form for stream-method selection.
DataForm form = new RequestForm();
HashSet <Option> options = new HashSet <Option>();
foreach (string opt in streamOptions)
{
options.Add(new Option(opt));
}
form.Fields.Add(new ListField("stream-method", true, null, null,
options));
// Wrap it in a 'feature' element to create the offer.
return(FeatureNegotiation.Create(form));
}
/// <summary>
/// Parses the selected stream-method from the specified 'feature' XML
/// element.
/// </summary>
/// <param name="feature">The 'feature' XML element.</param>
/// <returns>The stream method contained in the 'feature' XML
/// element.</returns>
/// <exception cref="ArgumentNullException">The feature parameter is
/// null.</exception>
/// <exception cref="ArgumentException">The feature element contains
/// invalid data.</exception>
private string ParseStreamMethod(XElement feature)
{
feature.ThrowIfNull("feature");
DataForm form = FeatureNegotiation.Parse(feature);
// The data-form must contain a field named 'stream-method'.
var field = form.Fields["stream-method"];
if (field == null)
{
throw new ArgumentException("Missing or erroneous 'stream-method' field.");
}
string selected = field.Values.FirstOrDefault();
if (selected == null)
{
throw new ArgumentException("No stream-method selected.");
}
return(selected);
}