/// <summary>
/// Downloads the specified syndication <paramref name="feeds"/> and merges them into an observable sequence.
/// </summary>
/// <param name="formatter">The object that reads each feed.</param>
/// <param name="feeds">The <see cref="Uri"/> objects identifying the feeds to be downloaded.</param>
/// <remarks>
/// <alert type="tip">
/// To get the original <see cref="SyndicationFeed"/> for each <see cref="SyndicationItem"/>, use the <see cref="SyndicationItem.SourceFeed"/> property.
/// </alert>
/// </remarks>
/// <returns>An observable sequence of items from all of the feeds merged together.</returns>
public static IObservable <SyndicationItem> DownloadObservable(this SyndicationFeedFormatter formatter, params Uri[] feeds)
{
Contract.Requires(formatter != null);
Contract.Requires(feeds != null);
Contract.Ensures(Contract.Result <IObservable <SyndicationItem> >() != null);
if (feeds.Length == 0)
{
return(Observable.Empty <SyndicationItem>());
}
else
{
return(formatter.DownloadObservable((IEnumerable <Uri>)feeds));
}
}
/// <summary>
/// Downloads all of the specified syndication <paramref name="feeds"/> at the specified <paramref name="interval"/> and merges them into an observable sequence.
/// </summary>
/// <param name="formatter">The object that reads each feed.</param>
/// <param name="client">The object used to make the web request.</param>
/// <param name="interval">The duration between downloads.</param>
/// <param name="feeds">The <see cref="Uri"/> objects identifying the feeds to be downloaded.</param>
/// <remarks>
/// <para>
/// <see cref="DownloadObservable(SyndicationFeedFormatter,TimeSpan,IEnumerable{Uri})"/> downloads all of the feeds upon subscription and then repeats the process at each <paramref name="interval"/>.
/// All of the <paramref name="feeds"/> are downloaded at each interval and merged into the observable sequence.
/// </para>
/// <para>
/// To avoid duplicate items, consider calling the <strong>Distinct</strong> method on the sequence. Alternatively, use the
/// <strong>Collect</strong> method to create an <see cref="System.Reactive.Subjects.IDictionarySubject{TKey,TValue}"/>.
/// </para>
/// <alert type="tip">
/// To get the original <see cref="SyndicationFeed"/> for each <see cref="SyndicationItem"/>, use the <see cref="SyndicationItem.SourceFeed"/> property.
/// </alert>
/// </remarks>
/// <returns>An observable sequence of items from all of the feeds merged together.</returns>
public static IObservable <SyndicationItem> DownloadObservable(this SyndicationFeedFormatter formatter, WebClient client, TimeSpan interval, IEnumerable <Uri> feeds)
{
Contract.Requires(formatter != null);
Contract.Requires(feeds != null);
Contract.Requires(interval >= TimeSpan.Zero);
Contract.Ensures(Contract.Result <IObservable <SyndicationItem> >() != null);
return((from _ in Observable.Timer(TimeSpan.Zero, interval)
#if !SILVERLIGHT
let uris = feeds
#else
let uris = feeds.EnsureNoCache()
#endif
select formatter.DownloadObservable(client, uris))
.Switch());
}
/// <summary>
/// Downloads all of the specified syndication <paramref name="feeds"/> at the specified <paramref name="interval"/> and merges them into an observable sequence.
/// </summary>
/// <param name="formatter">The object that reads each feed.</param>
/// <param name="client">The object used to make the web request.</param>
/// <param name="interval">The duration between downloads.</param>
/// <param name="feeds">The <see cref="Uri"/> objects identifying the feeds to be downloaded.</param>
/// <remarks>
/// <para>
/// <see cref="DownloadObservable(SyndicationFeedFormatter,TimeSpan,Uri[])"/> downloads all of the feeds upon subscription and then repeats the process at each <paramref name="interval"/>.
/// All of the <paramref name="feeds"/> are downloaded at each interval and merged into the observable sequence.
/// </para>
/// <para>
/// To avoid duplicate items, consider calling the <strong>Distinct</strong> method on the sequence. Alternatively, use the
/// <strong>Collect</strong> method to create an <see cref="System.Reactive.Subjects.IDictionarySubject{TKey,TValue}"/>.
/// </para>
/// <alert type="tip">
/// To get the original <see cref="SyndicationFeed"/> for each <see cref="SyndicationItem"/>, use the <see cref="SyndicationItem.SourceFeed"/> property.
/// </alert>
/// </remarks>
/// <returns>An observable sequence of items from all of the feeds merged together.</returns>
public static IObservable <SyndicationItem> DownloadObservable(this SyndicationFeedFormatter formatter, WebClient client, TimeSpan interval, params Uri[] feeds)
{
Contract.Requires(formatter != null);
Contract.Requires(client != null);
Contract.Requires(feeds != null);
Contract.Requires(interval >= TimeSpan.Zero);
Contract.Ensures(Contract.Result <IObservable <SyndicationItem> >() != null);
if (feeds.Length == 0)
{
return(Observable.Empty <SyndicationItem>());
}
else
{
return(formatter.DownloadObservable(client, interval, (IEnumerable <Uri>)feeds));
}
}
