/// <summary>
/// Performs a subsequent ordering of the elements in a sequence in ascending order according to a key.
/// </summary>
/// <typeparam name="TSource">The type of the elements of <paramref name="source"/>.</typeparam>
/// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
/// <param name="source">A sequence of values to order.</param>
/// <param name="keySelector">A function to extract a key from an element.</param>
/// <returns>An <see cref="IOrderedObservable{TSource}"/> whose elements are sorted according to a key.</returns>
public static IOrderedObservable <TSource> ThenBy <TSource, TKey>(
this IOrderedObservable <TSource> source,
Func <TSource, TKey> keySelector)
{
Contract.Requires(source != null);
Contract.Requires(keySelector != null);
Contract.Ensures(Contract.Result <IOrderedObservable <TSource> >() != null);
return(source.CreateOrderedObservable(keySelector, comparer: null, descending: false));
}
/// <summary>
/// Performs a subsequent ordering of the elements in a sequence in descending order according to the times at which corresponding observable sequences complete.
/// </summary>
/// <typeparam name="TSource">The type of the elements of <paramref name="source"/>.</typeparam>
/// <typeparam name="TOther">The type of the elements in the observable returned by <paramref name="keySelector"/>.</typeparam>
/// <param name="source">A sequence of values to order.</param>
/// <param name="keySelector">A function that returns an observable for an element indicating the time at which that element should appear in the ordering, by completing.</param>
/// <returns>An <see cref="IOrderedObservable{TSource}"/> whose elements are sorted in descending order according to the times at which corresponding observable sequences complete..</returns>
public static IOrderedObservable <TSource> ThenByDescending <TSource, TOther>(
this IOrderedObservable <TSource> source,
Func <TSource, IObservable <TOther> > keySelector)
{
Contract.Requires(source != null);
Contract.Requires(keySelector != null);
Contract.Ensures(Contract.Result <IOrderedObservable <TSource> >() != null);
return(source.CreateOrderedObservable(keySelector, descending: true));
}
