RSS Feed is very popular in Internet. This tutorial will show you how to create a RSS Reader using ASP.NET 2.0 and VB.NET.
RSS Reader using ASP.NET 2.0 and VB.NET 2005
RSS Feed is very popular in Internet. This tutorial will show you how to create a RSS Reader using ASP.NET 2.0 and VB.NET.
At first, import the namespace of System.Net, System.IO, and System.Xml
Imports System.Net
Imports System.IO
Imports System.Xml |
In this sample, we created a simple function to process the RSS feed
from a sample URL. This function define a string of rssURL as its
parameter. This string contains the RSS's URL. It will use the value of
rssURL to create a WebRequest.
WebRequest is the abstract base
class for the .NET Framework's request/response model for accessing
data from the Internet. An application that uses the request/response
model can request data from the Internet in a protocol-agnostic manner,
in which the application works with instances of the WebRequest class
while protocol-specific descendant classes carry out the details of the
request.
Requests are sent from an application to a particular
URI, such as a Web page on a server. The URI determines the proper
descendant class to create from a list of WebRequest descendants
registered for the application. WebRequest descendants are typically
registered to handle a specific protocol, such as HTTP or FTP, but can
be registered to handle a request to a specific server or path on a
server.
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The
response to this request will be put into WebResponse object. The
WebResponse class is the abstract base class from which
protocol-specific response classes are derived. Applications can
participate in request and response transactions in a protocol-agnostic
manner using instances of the WebResponse class while protocol-specific
classes derived from WebResponse carry out the details of the request.
Client applications do not create WebResponse objects directly; they
are created by calling the GetResponse method on a WebRequest instance.
After
then, the WebResponse object will be used to create a stream to get the
XML data. Stream is the abstract base class of all streams. A stream is
an abstraction of a sequence of bytes, such as a file, an input/output
device, an inter-process communication pipe, or a TCP/IP socket. The
Stream class and its derived classes provide a generic view of these
different types of input and output, isolating the programmer from the
specific details of the operating system and the underlying devices.
The we used a XmlDocument to store the stream data. XmlDocument
manipulating the data of XML, finally read the RSS contents from Feed.
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim rssURL As String = "http://www.codeguru.com/icom_includes/feeds/codeguru/rss-all.xml"
Response.Write("<font size=5><b>Site: " + rssURL + "</b></font><br />")
ProcessRSSItem(rssURL)
Response.Write("<hr />")
rssURL = "http://www.developer.com/icom_includes/feeds/special/dev-5.xml"
Response.Write("<font size=5><b>Site: " + rssURL + "</b></font><br />")
Call ProcessRSSItem(rssURL)
End Sub
Private Sub ProcessRSSItem(ByVal rssURL As String)
Dim myRequest As WebRequest = System.Net.WebRequest.Create(rssURL)
Dim myResponse As WebResponse = myRequest.GetResponse()
Dim rssStream As Stream = myResponse.GetResponseStream()
Dim rssDoc As New XmlDocument()
rssDoc.Load(rssStream)
Dim rssItems As XmlNodeList = rssDoc.SelectNodes("rss/channel/item")
Dim title As String = ""
Dim link As String = ""
Dim description As String = ""
Dim i As Integer
For i = 0 To rssItems.Count - 1
Dim rssDetail As XmlNode
rssDetail = rssItems.Item(i).SelectSingleNode("title")
If rssDetail.Equals(Nothing) = False Then
title = rssDetail.InnerText
Else
title = ""
End If
rssDetail = rssItems.Item(i).SelectSingleNode("link")
If rssDetail.Equals(Nothing) = False Then
link = rssDetail.InnerText
Else
link = ""
End If
rssDetail = rssItems.Item(i).SelectSingleNode("description")
If rssDetail.Equals(Nothing) = False Then
description = rssDetail.InnerText
Else
description = ""
End If
Response.Write("<p><b><a href='" + link + "' target='new'>" + title + "</a></b><br/>")
Response.Write(description + "
")
Next
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The front end Default.aspx page looks something like this:
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>RSS</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<fieldset style="height: 383px">
<legend><strong>RSS</strong></legend><br />
</fieldset>
</div>
</form>
</body>
</html> |
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The flow for the code behind page as follows.
Imports System.Net
Imports System.IO
Imports System.Xml
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim rssURL As String = "http://www.codeguru.com/icom_includes/feeds/codeguru/rss-all.xml"
Response.Write("<font size=5><b>Site: " + rssURL + "</b></font><br />")
ProcessRSSItem(rssURL)
Response.Write("<hr />")
rssURL = "http://www.developer.com/icom_includes/feeds/special/dev-5.xml"
Response.Write("<font size=5><b>Site: " + rssURL + "</b></font><br />")
Call ProcessRSSItem(rssURL)
End Sub
Private Sub ProcessRSSItem(ByVal rssURL As String)
Dim myRequest As WebRequest = System.Net.WebRequest.Create(rssURL)
Dim myResponse As WebResponse = myRequest.GetResponse()
Dim rssStream As Stream = myResponse.GetResponseStream()
Dim rssDoc As New XmlDocument()
rssDoc.Load(rssStream)
Dim rssItems As XmlNodeList = rssDoc.SelectNodes("rss/channel/item")
Dim title As String = ""
Dim link As String = ""
Dim description As String = ""
Dim i As Integer
For i = 0 To rssItems.Count - 1
Dim rssDetail As XmlNode
rssDetail = rssItems.Item(i).SelectSingleNode("title")
If rssDetail.Equals(Nothing) = False Then
title = rssDetail.InnerText
Else
title = ""
End If
rssDetail = rssItems.Item(i).SelectSingleNode("link")
If rssDetail.Equals(Nothing) = False Then
link = rssDetail.InnerText
Else
link = ""
End If
rssDetail = rssItems.Item(i).SelectSingleNode("description")
If rssDetail.Equals(Nothing) = False Then
description = rssDetail.InnerText
Else
description = ""
End If
Response.Write("<p><b><a href='" + link + "' target='new'>" + title + "</a></b><br/>")
Response.Write(description + "
")
Next
End Class |
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