In this article, we will see how to read and filter the RSS Feed of codetechblog.blogspot.com using LINQ to XML. We will first read the RSS feed and populate the DropDownList with ‘Authors’ retrieved from the feed. We will then filter the feed results based on the Author selected in the DropDownList.
e will be reading and filtering the RSS feed of this site codetechblog.blogspot.com. The RSS feed can be obtained over here http://feeds.feedburner.com/codetechblog. Let us quickly jump to the solution.
Step 1: Create a new website (Open Visual Studio > File > New Website) called ‘FilterRSS.
Step 2: Drag and drop a GridView and a DropDownList control to the page.
Step 3: Once you visit the RSS Feed over here, right click on the page and View Source. You will find an XML file, since RSS is an XML file.
Let us now write a LINQ to XML query to read the Title, Link, Description and Author elements from our RSS Feed and filter the results. Add the following markup to the DropDownList and some template Columns to the GridView, to display content:
<div>
<asp:DropDownList ID="DropDownList1" runat="server"
onselectedindexchanged="DropDownList1_SelectedIndexChanged"
AutoPostBack="True">
</asp:DropDownList>
<br /><br />
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:TemplateField HeaderText="Title">
<ItemTemplate>
<a href='<%# Eval("link") %>' target="_blank"><%# Eval("title") %></a>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Author"
HeaderText="Author" />
<asp:BoundField DataField="description" HtmlEncode="false"
HeaderText="Description" />
</Columns>
</asp:GridView>
</div>
Step 4: Now create an ArticlesList class which will act as a container for the items read from the feed
VB.NET
Public Class ArticlesList
Private privateTitle As String
Public Property Title() As String
Get
Return privateTitle
End Get
Set(ByVal value As String)
privateTitle = value
End Set
End Property
Private privateLink As String
Public Property Link() As String
Get
Return privateLink
End Get
Set(ByVal value As String)
privateLink = value
End Set
End Property
Private privateDescription As String
Public Property Description() As String
Get
Return privateDescription
End Get
Set(ByVal value As String)
privateDescription = value
End Set
End Property
Private privateAuthor As String
Public Property Author() As String
Get
Return privateAuthor
End Get
Set(ByVal value As String)
privateAuthor = value
End Set
End Property
End Class
We are using Generics to return a strongly typed collection of IEnumerable
The code will look similar to the following:
VB.NET
Imports System
Imports System.Linq
Imports System.Xml.Linq
Imports System.Collections.Generic
Partial Public Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
If (Not IsPostBack) Then
Dim xFeed As XElement = XElement.Load("http://feeds.feedburner.com/netCurryRecentArticles")
Dim items As IEnumerable(Of ArticlesList) = From item In xFeed.Elements("channel").Elements("item") _
Select New ArticlesList
item.Element("description").Value, Author = item.Element("author").Value
item.Element("link").Value, Description = item.Element("description").Value, Author
item.Element("title").Value, Link = item.Element("link").Value, Description
Title = item.Element("title").Value, Link
'store items in a session
Session("feed") = items
Dim authors = items.Select(Function(p) p.Author).Distinct()
DropDownList1.DataSource = authors
DropDownList1.DataBind()
Dim selAuth As String = DropDownList1.SelectedValue
PopulateGrid(selAuth)
End If
End Sub
Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
Dim selAuth As String = DropDownList1.SelectedValue
PopulateGrid(selAuth)
End Sub
Protected Sub PopulateGrid(ByVal author As String)
Dim items = CType(Session("feed"), IEnumerable(Of ArticlesList))
If items IsNot Nothing Then
Dim filteredList = From p In items _
Where p.Author = author _
Select p
GridView1.DataSource = filteredList
GridView1.DataBind()
End If
End Sub
End Class
Note: Observe the !IsPostBack which populates the collection only once, thereby saving the list from getting populated on every pageload.
We then apply a filter on this collection and select distinct authors and bind the result to a DropDownList. The selected author is passed to the PopulateGrid() method where the session object is casted back to IEnumerable
Similarly as and when the users selects a new author from the DropDownList, the list gets filtered and only the articles belonging to that author is displayed. Here are some screenshots:
I hope this article was useful and I thank you for viewing it
