xslt and System.ServiceModel.Syndication -- asp.net

Paul
2/5/2008 4:17:03 AM

Steven,

Thanks for your input. I have tried your approach, and find that I get
errors on the transform. I have tried with various data sources, like the
names of folders in my music collecection etc. I get errors like:

"'<', hexadecimal value 0x3C, is an invalid attribute character. Line 1,
position ..."
or
"There is an unclosed literal string ...

How do I deal with these errors without cancelling the whole transform?

Thanks
Paul

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stcheng@online.microsoft.com
2/5/2008 9:52:02 AM

Hi Paul,

As for the rss transforming issue, I think you may consider the following
approach:

Since you originally write the Syndication object into XMLWriter and flush
out to ASP.NET page response, you can consider first write the RSS xml into
a memoryStream(wrappered through a XmlWriter). Then, you can use .NET XSLT
api to perform tranformation on the XML document in the memorystream(read
it through a StreamReader).

Here are some information about how to use XSLT transformation classes in
..NET 2.0:

#XSLT Transformations
http://msdn2.microsoft.com/en-us/library/14689742.aspx

#XSL Transformations in .NET 2.0
http://www.15seconds.com/issue/060608.htm

Hope this helps.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

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Martin Honnen
2/5/2008 3:43:06 PM

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Implement your own XmlWriter that writes out the xml-stylesheet
processing instruction. You can do that by subclassing XmlTextWriter for
instance.

Here is an example:

Public Class XmlStylesheetWriter : Inherits XmlTextWriter
Private written As Boolean
Private _type As String = "text/xsl"
Public Property Type() As String
Get
Return _type
End Get
Set(ByVal value As String)
_type = value
End Set
End Property

Private _href As String
Public Property Href() As String
Get
Return _href
End Get
Set(ByVal value As String)
_href = value
End Set
End Property

Public Sub New(ByVal w As System.IO.Stream, ByVal encoding As
System.Text.Encoding)
MyBase.New(w, encoding)
End Sub

Public Sub New(ByVal filename As String, ByVal encoding As
System.Text.Encoding)
MyBase.New(filename, encoding)
End Sub

Public Sub New(ByVal w As System.IO.TextWriter)
MyBase.New(w)
End Sub

Public Overrides Sub WriteStartDocument()
MyBase.WriteStartDocument()
WriteXmlStylesheetPI()
End Sub

Public Overrides Sub WriteStartDocument(ByVal standalone As
Boolean)
MyBase.WriteStartDocument(standalone)
WriteXmlStylesheetPI()
End Sub

Public Overrides Sub WriteStartElement(ByVal prefix As String,
ByVal localName As String, ByVal ns As String)
If Not (written) Then
WriteXmlStylesheetPI()
End If
MyBase.WriteStartElement(prefix, localName, ns)
End Sub

Private Sub WriteXmlStylesheetPI()
MyBase.WriteProcessingInstruction("xml-stylesheet",
String.Format("type=""{0}"" href=""{1}""", Type, Href))
written = True
End Sub
End Class

Used as follows:

Dim feed As New SyndicationFeed("Example feed", "This is an
example feed", New Uri("http://example.com/"))
Dim writer As New XmlStylesheetWriter(Console.Out)
writer.Href = "sheet.xsl"
writer.Formatting = Formatting.Indented

Dim formatter = feed.GetRss20Formatter(False)

formatter.WriteTo(writer)
writer.Close()

--

Martin Honnen --- MVP XML

stcheng@online.microsoft.com
2/7/2008 2:24:06 AM

Thanks for your reply Paul,

Regarding on the new error message you mentioned, there seems exist some
certain character that make the XSLT transformor complain about. I suggest
you first save the RSS XML document(get from the Syndication object) into a
xml file and then open it in IE to see whether IE will detect any well-form
validation error. You can also try using a simple RSS collection so that
you can also open the saved XML document and check it in some text editor.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

This posting is provided "AS IS" with no warranties, and confers no rights.

--------------------
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Paul
2/11/2008 2:53:03 AM

Hi guys,

Thanks for the input. My problems were in the underlying memory streams,
sorry but I can't recall the detail now.

Here is the final method I used to emit from my aspx page:

Private Sub WriteOutput()
Dim feed As SyndicationFeed = New SyndicationFeed
feed = GetARSFeed()
'feed = getDummyFeed()

Dim Title As TextSyndicationContent = New
TextSyndicationContent(_FeedInfo.FeedName)
Dim Description As TextSyndicationContent = New
TextSyndicationContent(_FeedInfo.FeedDescription)
feed.Title = Title
feed.Description = Description

Select Case _FeedInfo.OutputFormat
Case "Raw RSS"
Dim memstream As New MemoryStream
Dim rssWriter As XmlWriter = XmlWriter.Create(memstream)
Dim rssFormatter As Rss20FeedFormatter = New
Rss20FeedFormatter(feed)
rssFormatter.WriteTo(rssWriter)

rssWriter.Flush()

memstream.Seek(0, SeekOrigin.Begin)
Dim xslReader As XmlReader = XmlReader.Create(memstream)

Response.ContentType = "text/xml"
Dim r As New StreamReader(memstream)
memstream.Seek(0, SeekOrigin.Begin)
Response.Write(r.ReadToEnd)
Response.End()
Case "Raw ATOM"
Dim memstream As New MemoryStream
Dim rssWriter As XmlWriter = XmlWriter.Create(memstream)
Dim atomFormatter As Atom10FeedFormatter = New
Atom10FeedFormatter(feed)
atomFormatter.WriteTo(rssWriter)

rssWriter.Flush()

memstream.Seek(0, SeekOrigin.Begin)
Dim xslReader As XmlReader = XmlReader.Create(memstream)

Response.ContentType = "text/xml"
Dim r As New StreamReader(memstream)
memstream.Seek(0, SeekOrigin.Begin)
Response.Write(r.ReadToEnd)
Response.End()
Case "RSS Presented as Formatted HTTP"
Dim memstream As New MemoryStream
Dim rssWriter As XmlWriter = XmlWriter.Create(memstream)
Dim rssFormatter As Rss20FeedFormatter = New
Rss20FeedFormatter(feed)
rssFormatter.WriteTo(rssWriter)

rssWriter.Flush()

Dim xslt As New Xsl.XslCompiledTransform()
xslt.Load(_FeedInfo.XSLTFileName)

memstream.Seek(0, SeekOrigin.Begin)
Dim xslReader As XmlReader = XmlReader.Create(memstream)

Dim newmem As New MemoryStream
xslt.Transform(xslReader, Nothing, newmem)

Response.ContentType = "text/HTML"
Dim r As New StreamReader(newmem)
newmem.Seek(0, SeekOrigin.Begin)
Response.Write(r.ReadToEnd)
Response.End()
End Select

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stcheng@online.microsoft.com
2/12/2008 3:06:12 AM

Thanks for your followup.

I'm glad that you've got it working and also thanks for your sharing.

Have a nice day.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

This posting is provided "AS IS" with no warranties, and confers no rights.

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