public async Task <string> BuildRSSFeed(RSSFeedOptions rssOptions)
{
if (rssOptions == null)
{
throw new ArgumentNullException(nameof(rssOptions));
}
if (string.IsNullOrEmpty(rssOptions.Title))
{
throw new ArgumentNullException(nameof(rssOptions.Title));
}
return(await _memoryCache.GetOrCreateAsync(rssOptions.Caching?.Key ?? "RSSCache", async caching =>
{
caching.SetAbsoluteExpiration(rssOptions.Caching?.CacheDuration ?? TimeSpan.FromDays(1));
return await BuildRSSFeedInternal(rssOptions);
}));
}
private async Task <string> BuildRSSFeedInternal(RSSFeedOptions rssOptions)
{
var sb = new StringBuilder();
using (var _ = new StringWriter(sb))
using (XmlWriter xmlWriter = XmlWriter.Create(_, new XmlWriterSettings {
Async = true, Indent = true
}))
{
//Since the XmlWriter doesn't care about actually setting UTF-8, let's just do it manually
await xmlWriter.WriteProcessingInstructionAsync("xml", @"version=""1.0"" encoding=""UTF-8""");
var syndicationFeedWriter = new RssFeedWriter(xmlWriter);
await syndicationFeedWriter.WriteTitle(rssOptions.Title).ConfigureAwait(false);
if (!string.IsNullOrEmpty(rssOptions.Description))
{
await syndicationFeedWriter.WriteDescription(rssOptions.Description).ConfigureAwait(false);
}
if (rssOptions.Url != null)
{
await syndicationFeedWriter.Write(new SyndicationLink(rssOptions.Url)).ConfigureAwait(false);
if (rssOptions.ImageUrl != null)
{
await syndicationFeedWriter.Write(new SyndicationImage(rssOptions.ImageUrl)
{
Title = rssOptions.Title,
Link = new SyndicationLink(rssOptions.Url)
}).ConfigureAwait(false);
}
}
//Choose the current culture if no language has been chosen
await syndicationFeedWriter.WriteLanguage(rssOptions.Language ?? CultureInfo.CurrentCulture).ConfigureAwait(false);
if (!string.IsNullOrEmpty(rssOptions.ManagingEditor))
{
await syndicationFeedWriter.Write(new SyndicationPerson(null, rssOptions.ManagingEditor, RssContributorTypes.ManagingEditor)).ConfigureAwait(false);
}
//Do we even still care about Webmaster?
if (!string.IsNullOrEmpty(rssOptions.Webmaster))
{
await syndicationFeedWriter.WriteValue("webMaster", rssOptions.Webmaster).ConfigureAwait(false);
}
if (!string.IsNullOrEmpty(rssOptions.Copyright))
{
await syndicationFeedWriter.WriteCopyright(rssOptions.Copyright).ConfigureAwait(false);
}
var syndicationItems = await _rssProvider.RetrieveSyndicationItems().ConfigureAwait(false);
//Use the latest LastUpdated item in the list to determine the last build date.
await syndicationFeedWriter.WriteLastBuildDate(syndicationItems.Max(x => x.LastUpdated)).ConfigureAwait(false);
foreach (var __ in syndicationItems)
{
await syndicationFeedWriter.Write(__.ToSyndicationItem()).ConfigureAwait(false);
}
await xmlWriter.FlushAsync().ConfigureAwait(false);
}
return(sb.ToString());
}
public static IApplicationBuilder UseRSSFeed(this IApplicationBuilder builder, string path, RSSFeedOptions options)
{
return(builder.UseWhen(context => context.Request.Path.Value.ToLower() == path, config =>
{
config.UseMiddleware <RSSMiddleware>(path, options);
}));
}
public RSSMiddleware(RequestDelegate next, string urlPath, RSSFeedOptions rssOptions)
{
_next = next ?? throw new ArgumentNullException(nameof(next));
_urlPath = urlPath ?? throw new ArgumentNullException(nameof(urlPath));
_rssOptions = rssOptions;
}
