In my MVC Web Application, I developed a function to return a Newsstand Atom Feed (for Apple's Newsstand). One of their requirements for this feed is that it is effectively encoded in UTF-8 and must not include a BOM. This is how I coded my view (class names are fictional to preserve my company's privacy):
<%@ Page Language="VB" Inherits="System.Web.Mvc.ViewPage(Of IEnumerable (Of AtomFeed))" ContentType="application/atom+xml" ResponseEncoding="UTF-8" %><?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:news="http://itunes.apple.com/2011/Newsstand"><%="" %><% If Not Model Is Nothing Then%><% Dim updateDate As String = ViewData("feedUpdate")%><% If (Not String.IsNullOrEmpty(updateDate)) Then%>
<updated><%= updateDate %></updated><%
End If%><% For Each f In Model%>
<entry>
<id><%= f.id%></id>
<updated><%= f.updated%></updated>
<published><%= f.published%></published>
<news:end_date><%= f.endDate%></news:end_date>
<summary><%= f.summaryText%></summary>
<news:cover_art_icons>
<news:cover_art_icon size="SOURCE" src="<%= f.newspaperCover %>"/>
</news:cover_art_icons>
</entry><%
Next%><%
End If%>
</feed>
Today we received a mail from itunes complaining that they couldn't import our XML, without a clue as to why it failed. The rendered XML is compliant to their requirements so my only guess is that there is a problem with the encoding of my view.
How do I correctly return this view in UTF-8 without BOM, so that when they pull the XML from my given url, it will be processed correctly?
EDIT:
After using Darin's implementation, I ended up with the following feed
<?xml version="1.0" encoding="utf-8"?>
<feed xmlns:news="http://itunes.apple.com/2011/Newsstand"
xmlns="http://www.w3.org/2005/Atom">
<title type="text"></title>
<id>uuid:5fc48c36-a1d3-4280-a856-a1a0528e2552;id=1</id>
<updated>2012-07-23T00:40:00Z</updated>
<entry>
<id>23.07.2012</id>
<title type="text"></title>
<summary type="text">...</summary>
<updated>2012-07-23T00:40:00Z</updated>
<published xmlns="">2012-07-23T00:40:00Z</published>
<news:end_date>2012-07-24T00:40:00Z</news:end_date>
<news:cover_art_icons>
<news:cover_art_icon size="SOURCE"
src="https://www.someurl.com" />
</news:cover_art_icons>
</entry>
<entry>
<id>22.07.2012</id>
<title type="text"></title>
<summary type="text">...</summary>
<updated>2012-07-22T00:40:00Z</updated>
<published xmlns="">2012-07-22T00:40:00Z</published>
<news:end_date>2012-07-23T00:40:00Z</news:end_date>
<news:cover_art_icons>
<news:cover_art_icon size="SOURCE"
src="https://www.someurl.com" />
</news:cover_art_icons>
</entry>
</feed>
Now Apple's Newsstand cannot import the following feed because they say they can't find element in this feed's entry element.
Instead of generating the an XML feed manually in a view I would recommend you using the SyndicationFeed class which is designed for that purpose.
So let's assume that you have some domain model representing your data:
public class NewsstandFeed
{
public DateTime? Updated { get; set; }
public IEnumerable<AtomFeed> Items { get; set; }
}
public class AtomFeed
{
public int Id { get; set; }
public DateTime Updated { get; set; }
public DateTime Published { get; set; }
public DateTime EndDate { get; set; }
public string SummaryText { get; set; }
public string NewspaperCover { get; set; }
}
and then a controller that will query some DAL to retrieve the domain model:
public class HomeController : Controller
{
public ActionResult Index()
{
// Normally this will come from a database or something,
// but I am hardcoding it for demonstration purposes here
var model = new NewsstandFeed
{
Updated = DateTime.Now,
Items = new[]
{
new AtomFeed
{
Id = 1,
Updated = DateTime.Now,
Published = DateTime.Now,
EndDate = DateTime.Now,
SummaryText = "some summary",
NewspaperCover = "http://www.google.com"
}
}
};
return new NewsstandFeedResult(model);
}
}
Notice the NewsstandFeedResult that the controller action returns? Let's implement it:
public class NewsstandFeedResult : ActionResult
{
public const string NewsstandNS = "http://itunes.apple.com/2011/Newsstand";
public NewsstandFeed Model { get; private set; }
public NewsstandFeedResult(NewsstandFeed model)
{
Model = model;
if (model.Items == null)
{
model.Items = Enumerable.Empty<AtomFeed>();
}
}
public override void ExecuteResult(ControllerContext context)
{
var response = context.HttpContext.Response;
response.ContentType = "application/atom+xml";
var feed = new SyndicationFeed();
var n = new XmlQualifiedName("news", "http://www.w3.org/2000/xmlns/");
XNamespace newsstandNs = NewsstandNS;
feed.AttributeExtensions.Add(n, newsstandNs.ToString());
if (Model.Updated.HasValue)
{
feed.LastUpdatedTime = new DateTimeOffset(Model.Updated.Value.ToUniversalTime());
}
var items = new List<SyndicationItem>();
foreach (var item in Model.Items)
{
var si = new SyndicationItem();
si.Id = item.Id.ToString();
si.LastUpdatedTime = new DateTimeOffset(item.Updated.ToUniversalTime());
si.Summary = new TextSyndicationContent(item.SummaryText);
si.ElementExtensions.Add(new XElement(newsstandNs + "end_date", item.EndDate.ToUniversalTime()));
si.ElementExtensions.Add(
new XElement(
newsstandNs + "cover_art_icons",
new XElement(
newsstandNs + "cover_art_icon",
new XAttribute("size", "SOURCE"),
new XAttribute("src", item.NewspaperCover)
)
)
);
items.Add(si);
}
feed.Items = items;
using (var writer = XmlWriter.Create(response.OutputStream))
{
var formatter = new Atom10FeedFormatter(feed);
formatter.WriteTo(writer);
}
}
}
That's it. Now simply navigate to /home/index and you will get a valid Atom feed respecting all industry standards so that you don't have to worry about BOMs and stuff.