Introduction

Some time ago Peter Bromberg wrote an article to convert an Atom feed to a RSS feed. In this code-snipp you will learn how to do the opposite - we will convert a simple RSS feed to an Atom feed.

RSS to Atom

As mentioned in the introduction, the original idea came with writing of an article by Peter Bromberg. The article can be found here. Like the code displayed in Peter's article this snipp uses the basic Xml classes for the conversion. The code is straight forward - I created a simple class, that you can use to convert the RSS feed to Atom.

Code

Imports System.IO
Imports System.Xml
Imports Microsoft.VisualBasic

Public Class FeedConverter

    Public Shared Function ConvertRssToAtom(ByVal strRssFeedURL As String) As StringWriter
        Dim xmlDoc As New XmlDocument()
        xmlDoc.Load(strRssFeedURL)

        ' title, link, date
        Dim strTitle As String = xmlDoc.SelectSingleNode("rss/channel/title").InnerText
        Dim strLink As String = xmlDoc.SelectSingleNode("rss/channel/link").InnerText
        Dim dtUpdatedDate As DateTime = Convert.ToDateTime(xmlDoc.SelectSingleNode("rss/channel/pubDate").InnerText)

        ' author info:
        Dim node As XmlNode = xmlDoc.SelectSingleNode("rss/channel/managingEditor")
        Dim strManagingEditor As String = String.Empty
        If Not node Is Nothing Then
            strManagingEditor = node.InnerText
        End If

        Dim sw As StringWriter = New StringWriter
        Dim ms As New MemoryStream
        Dim atomWriter As New XmlTextWriter(sw)
        atomWriter.Formatting = Formatting.Indented
        atomWriter.WriteStartDocument(True)

        atomWriter.WriteStartElement("feed")
        atomWriter.WriteAttributeString("xmlns", "http://www.w3.org/2005/Atom")

        ' write title, link and date
        atomWriter.WriteElementString("title", strTitle)
        atomWriter.WriteElementString("link", strLink)
        atomWriter.WriteElementString("updated", dtUpdatedDate.ToString("s"))

        ' write author info
        atomWriter.WriteStartElement("author")
        atomWriter.WriteElementString("name", strTitle)
        atomWriter.WriteElementString("email", strManagingEditor)
        atomWriter.WriteEndElement()
        atomWriter.WriteElementString("id", strLink) ' RSS feeds doesnt really have any id element

        Dim gNode As XmlNode = Nothing
        For Each entryNode As XmlNode In xmlDoc.SelectNodes("rss/channel/item")
            atomWriter.WriteStartElement("entry")
            atomWriter.WriteElementString("title", entryNode.SelectSingleNode("title").InnerText)
            atomWriter.WriteElementString("link", entryNode.SelectSingleNode("link").InnerText)

            gNode = entryNode.SelectSingleNode("guid")
            If Not gNode Is Nothing Then
                atomWriter.WriteElementString("id", gNode.InnerText)
            Else
                atomWriter.WriteElementString("id", entryNode.SelectSingleNode("link").InnerText)
            End If

            atomWriter.WriteEndElement()
        Next

        atomWriter.WriteEndElement()
        atomWriter.WriteEndDocument()
        Return sw
    End Function

End Class

Usage

To convert the class simply use the ConvertRssToAtom class and you are ready to go. Here an example:

Response.ContentType = "text/xml"
Response.Write(FeedConverter.ConvertRssToAtom("http://blogs.law.harvard.edu/tech/xml/rss.xml").ToString)
Response.End()

Summary

This quick code-snippet explained how you can convert an RSS feed to ATOM.

Downloads

Class AtomToRssConverter

About Sonu Kapoor

Sonu Kapoor is the creator of DotNetSlackers. Originally started in 2005, DotNetSlackers is a website to help developers stay up-to-date with the latest developments in .NET. During the sites’ youth DotNetSlackers focused solely on .NET news aggregation; however, over the years DotNetSlackers has gr... View complete profile