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How to create your own RSS Reader - .net RSS (C#/VB.NET) implementations




Download the demo code

There is a number of ways to read a RSS feed in .net, I am going to look at four different solutions to do this.

The following code is by no means a mature solution (it assumes a lot of things), and should soley be used as a starting point - ensure that you've got sufficient exception handling.

Looking at the namespaces, we'll be using a generic list (System.Collections.Generic) for our items, which we can easily bind to a datasource.

We're going to have a look at using Linq (System.Linq & System.Xml.Linq), and have a look at Microsofts' WCF syndication (System.ServiceModel.Syndication - which you can find in the System.ServiceModel.Web component in .net 3.5)

C#

 
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel.Syndication;
using System.Xml;
using System.Xml.Linq;
 

VB.net

 
Imports System.Collections.Generic
Imports System.Linq
imports System.ServiceModel.Syndication
imports System.Xml
imports System.Xml.Linq
 

a simple struct/structure, which will contain the rss items

C#

 
public struct RSSItem
{
    private string _title;
    public string title
    {
        get
        {
            return _title;
        }
        set
        {
            _title = value;
        }
    }
 
    private string _link;
    public string link
    {
        get
        {
            return _link;
        }
        set
        {
            _link = value;
        }
    }
 
    private string _description;
    public string description
    {
        get
        {
            return _description;
        }
        set
        {
            _description = value;
        }
    }
}
 

VB.net

 
Public Structure RSSItem
    Private _title As String
    Public Property title() As String
        Get
            Return _title
        End Get
        Set(ByVal value As String)
            _title = value
        End Set
    End Property
 
    Private _link As String
    Public Property link() As String
        Get
            Return _link
        End Get
        Set(ByVal value As String)
            _link = value
        End Set
    End Property
 
    Private _description As String
    Public Property description() As String
        Get
            Return _description
        End Get
        Set(ByVal value As String)
            _description = value
        End Set
    End Property
End Structure
 

Using the XmlDocument class

C#

 
public class RSSReader
{
    public string title;
    public string link;
    public string description;
    public List<RSSItem> items = new List<RSSItem>();
 
    public RSSReader(string url)
    {
        XmlDocument doc = new XmlDocument();
        doc.Load(url);
 
        XmlElement channel = doc["rss"]["channel"];
        XmlNodeList items = channel.GetElementsByTagName("item");
        this.title = channel["title"].InnerText;
        this.link = channel["link"].InnerText;
        this.description = channel["description"].InnerText;
 
        foreach (XmlNode item in items)
        {
            RSSItem rssItem = new RSSItem();
            rssItem.title = item["title"].InnerText;
            rssItem.description = item["description"].InnerText;
            rssItem.link = item["link"].InnerText;
            this.items.Add(rssItem);
        }
    }
}
 

VB.net

 
Public Class RSSReader
 
    Public title As String
    Public link As String
    Public description As String
    Public items As List(Of RSSItem) = New List(Of RSSItem)()
 
    Public Sub New(ByVal url As String)
 
        Dim doc As New XmlDocument()
        doc.Load(url)
 
        Dim channel As XmlElement = doc("rss")("channel")
        Dim items As XmlNodeList = channel.GetElementsByTagName("item")
        Me.title = channel("title").InnerText
        Me.link = channel("link").InnerText
        Me.description = channel("description").InnerText
 
        For Each item As XmlNode In items
            Dim rss As New RSSItem()
            rss.title = item("title").InnerText
            rss.description = item("description").InnerText
            rss.link = item("link").InnerText
            Me.items.Add(rss)
        Next
 
    End Sub
End Class
 

Reading RSS feed using linq

C#

 
public class RSSReader
{
    public string title;
    public string link;
    public string description;
    public List<RSSItem> items;
 
    public RSSReader(string url)
    {
        XElement rssFeed = XElement.Load(url).Element("channel");
        this.title = rssFeed.Element("title").Value;
        this.link = rssFeed.Element("link").Value;
        this.description = rssFeed.Element("description").Value;
        items = (from Item in rssFeed.Elements("item")
                 select new RSSItem()
                 {
                     title = Item.Element("title").Value,
                     description = Item.Element("description").Value,
                     link = Item.Element("link").Value
                 }).ToList<RSSItem>();
    }
}
 

VB.net

 
Public Class RSSReader
 
    Public title As String
    Public link As String
    Public description As String
    Public items As List(Of RSSItem)
 
    Public Sub New(ByVal url As String)
 
        Dim rssFeed As XElement = XElement.Load(url).Element("channel")
        Me.title = rssFeed.Element("title").Value
        Me.link = rssFeed.Element("link").Value
        Me.description = rssFeed.Element("description").Value
 
        items = (From Item In rssFeed.Elements("item") _
                 Select New RSSItem With { _
                    .title = Item.Element("title").Value, _
                    .description = Item.Element("description").Value, _
                    .link = Item.Element("link").Value}).ToList()
 
    End Sub
 
End Class
 

Using the XmlTextReader class envolves a bit more work, but this is the route you can go if you're thinking about .net 1.1 support (obviously stripping generics from this solution, since generics only appeared in .net in version 2.0)

C#

 
public class RSSReader
{
    public string title;
    public string link;
    public string description;
    public List<RSSItem> items = new List<RSSItem>();
 
    public RSSReader(string url)
    {
        XmlTextReader reader = new XmlTextReader(url);
 
        while (reader.Read())
        {
            if (reader.NodeType == XmlNodeType.Element)
            {
                switch (reader.Name)
                {
                    case "title":
                        this.title = reader.ReadString();
                        break;
                    case "link":
                        this.link = reader.ReadString();
                        break;
                    case "description":
                        this.description = reader.ReadString();
                        break;
                    case "image":
                        while (!((reader.Name == "image") &&
                                    (reader.NodeType == XmlNodeType.EndElement)) &&
                                            reader.Read()) 
                        break;
                }
            }
 
            if (reader.Name == "item")
            {
                RSSItem item = new RSSItem();
                while (!((reader.Name == "item") &&
                            (reader.NodeType == XmlNodeType.EndElement)) &&
                                reader.Read())
                {
                    if (reader.NodeType == XmlNodeType.Element)
                    {
                        switch (reader.Name.ToLower())
                        {
                            case "title":
                                item.title = reader.ReadString();
                                break;
                            case "description":
                                item.description = reader.ReadString();
                                break;
                            case "link":
                                item.link = reader.ReadString();
                                break;
                        }
                    }
                }
                items.Add(item);
            }
        }
    }
}
 

VB.net

 
Public Class RSSReader
 
    Public title As String
    Public link As String
    Public description As String
    Public items As List(Of RSSItem) = New List(Of RSSItem)()
 
    Public Sub New(ByVal url As String)
 
        Dim reader As New XmlTextReader(url)
 
        While reader.Read()
            If reader.NodeType = XmlNodeType.Element Then
                Select Case (reader.Name)
                    Case "title"
                        Me.title = reader.ReadString()
                    Case "link"
                        Me.link = reader.ReadString()
                    Case "description"
                        Me.description = reader.ReadString()
                    Case "image"
                        While (Not ((reader.Name = "image") And _
                                    (reader.NodeType = XmlNodeType.EndElement)) And _
                                            reader.Read())
                        End While
                End Select
            End If
 
            If reader.Name = "item" Then
 
                Dim item As New RSSItem()
                While (Not ((reader.Name = "item") And _
                            (reader.NodeType = XmlNodeType.EndElement)) And _
                                reader.Read())
                    If (reader.NodeType = XmlNodeType.Element) Then
 
                        Select Case (reader.Name.ToLower())
                            Case "title"
                                item.title = reader.ReadString()
                            Case "description"
                                item.description = reader.ReadString()
                            Case "link"
                                item.link = reader.ReadString()
                        End Select
                    End If
                End While
                items.Add(item)
            End If
        End While
    End Sub
 

.net 3.5 "shipped", with WCF(Windows Communication Foundation), which contains classes for generating rss 2.0 feeds and formatting them - the only con is, theses classes dont support previous rss specifications (some which are widely still in use)

C#

 
XmlReader RSSReader = XmlReader.Create(@"http://rss.cnn.com/rss/cnn_space.rss");
Rss20FeedFormatter formatter = new Rss20FeedFormatter();
formatter.ReadFrom(RSSReader);
 

VB.net

 
Dim RSSReader As XmlReader = XmlReader.Create("http://rss.cnn.com/rss/cnn_space.rss")
Dim formatter As Rss20FeedFormatter = New Rss20FeedFormatter()
formatter.ReadFrom(RSSReader)
 

Other solutions

There are many other ways to parse RSS feeds in .net, generated xsd classes (serliaze/deserializing rss feeds to it using xmlserializer), using a dataset (although you might run into some schema issues), using it as a xmldatasource, using xsl(in a server side manner, client side if you dont mind cross browser compatibility) and many others.



Posted by - Christoff Truter
Created - 2008-06-23 13:18:25


Comments

re: Show Items in the RssReader

Hi Buck In you're iteration you're adding the title of the main object - eg myItems.title, simply change it to rss.title (since thats the instance of each iterated collection) eg Dim myItems As New rsi.RSSReader(txtURL.Text) For Each rss In myItems.items ListBox1.Items.Add(rss.title) Next


Posted by - Christoff Truter
Created - 2009-09-17 06:34:01

Show Items in the RssReader

Thank you for this code sample. It is exactly what I was looking for. I am having an issue with that I am hoping you can help me with. I am trying to add the individual RSS posts into a listbox. This adds the title of the forum for each post put I want to add the title of the post into it. What am I missing? Dim myItems As New rsi.RSSReader(txtURL.Text) For Each rss In myItems.items ListBox1.Items.Add(myItems.title) Next


Posted by - Buck Hicks
Created - 2009-09-17 05:32:00



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