/QDFeedParser/FileSystemFeedFactory.cs

using System;

using System.IO;

using QDFeedParser.Xml;



namespace QDFeedParser

{

    public partial class FileSystemFeedFactory : BaseFeedFactory

    {

        public FileSystemFeedFactory()

            : this(new LinqFeedXmlParser())

        { }



        public FileSystemFeedFactory(IFeedXmlParser parser)

            : this(parser, null)

        { }



        public FileSystemFeedFactory(IFeedInstanceProvider instanceProvider)

            : this(new LinqFeedXmlParser(), instanceProvider)

        { }



        public FileSystemFeedFactory(IFeedXmlParser parser, IFeedInstanceProvider instanceProvider)

            : base(parser, instanceProvider)

        { }



        public override bool PingFeed(Uri feeduri)

        {

            return File.Exists(feeduri.LocalPath);

        }



        public override string DownloadXml(Uri feeduri)

        {

            if (!this.PingFeed(feeduri)) throw new MissingFeedException(string.Format("Was unable to open local XML file {0}", feeduri.LocalPath));



            return DownloadXmlFromUri(feeduri).FeedContent;

        }



        //Hacking asynchronous file IO just to make the interface consistent - there's not much performance benefit otheriwse

        public override IAsyncResult BeginDownloadXml(Uri feeduri, AsyncCallback callback)

        {

            if (!this.PingFeed(feeduri)) throw new MissingFeedException(string.Format("Was unable to open local XML file {0}", feeduri.LocalPath));



            return FeedWorkerDelegate.BeginInvoke(feeduri, callback, new FeedTuple());



        }



        public override FeedTuple EndDownloadXml(IAsyncResult asyncResult)

        {

            var result = FeedWorkerDelegate.EndInvoke(asyncResult);

            return result;

        }





        protected readonly FileIOWorker FeedWorkerDelegate = new FileIOWorker(DownloadXmlFromUri);



        protected delegate FeedTuple FileIOWorker(Uri feeduri);



        /// <summary>

        /// Requires a valid uri on local disk - otherwise the method will promptly fail.

        /// </summary>

        /// <param name="feeduri">A valid uri on local disk</param>

        /// <returns>The xml content of the uri</returns>

        protected static FeedTuple DownloadXmlFromUri(Uri feeduri)

        {

            string xmlContent;

            using (var reader = new StreamReader(feeduri.OriginalString))

            {

                xmlContent = reader.ReadToEnd();

            }



            return new FeedTuple { FeedContent = xmlContent, FeedUri = feeduri };

        }

    }

}