Consuming URL Shortening Services in VB.NET

Overview

Just another article of the URL shortening services series.

Today, we are going to talk about another hot and easy-to-use service, it's Tweetburner. If you haven't used it before, then it's the time to.

We're going to discuss how to use Tweetburner first. After that, we'll inspect its API and learn how to use it in your .NET application.

Introduction

Again, one of the most popular URL shortening services ever.

Today is dedicated for Tweetburner (known as twurl,) one of the hot, simple, and easy-to-use shortening services that you can compare to is.gd.

Description

When you visit Tweetburner website (via http://tweetburner.com or http://twurl.nl,) you can see that it allows users to register to gain more functionalities (specifically, link analytics.) However, at the time of this writing, the account page is disabled for technical issues and nothing interesting would happen if you register there.

One of the hot features of Tweetburner is that it allows you to post your links to twitter (you guessed) and friendfeed as soon as they're shortened just click 'Share this link' before you leave the page.

 

Unfortunately, you can't benefit from this sharing feature programmatically, but of course, you can create your own routines.

After shrinking your URL, you get a new short link about 22 characters long (18 in is.gd) prefixed with http://twurl.nl.

API

Actually, Tweetburner doesn't help you with an API. Instead, it provides you with a simple web page (used for shortening URLs) that you can access it from your code and get your short URLs.

Let's try it! Browse to our key page, http://tweetburner.com/links, and push your long URL and click the shortening button.

[caption id="attachment_2805" align="alignnone" width="500" caption="Figure 3 - Shortening Links API, Tweetburner"]



[/caption]

So how you can access this page via your .NET application and fill in its single field? Let's get the idea! If you check the API documentation page, you might find that you are required just torequest information from that page, post it the required URL via a simple string included in the request body, link[url]={0} (where {0} is the long URL, and just wait for the response that would contain the short URL of course if the function succeed.

Do you find that 'link[url]={0}' strange? Try this with me! Browse to our page,http://tweetburner.com/links, and save it as HTML in your PC (not required, just grab its HTML code.)

Sure we are interested on this magical text box, so scroll down to its definition that looks like this:

<input id="link_url" name="link[url]" size="30" type="text" />

Notice that the text box is given the name 'link[url]', that's why we push 'link[url]={0}' on the request body. Given that hot information, you can push any data to any web form, just get the information required.

Now, let's code! The next function browses to our page, http://tweetburner.com/links, pushes the long URL specified, and gets the short URL back from the server. (Remember to include the namespace System.Net for the code to work properly.)

VB.NET

    Function Shorten(ByVal url As String) As String
        url = Uri.EscapeUriString(url)

        Dim req As HttpWebRequest = _
            CType(WebRequest.Create("http://tweetburner.com/links"), HttpWebRequest)
        req.Timeout = 5000
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
 
        Dim buffer() As Byte = _
            System.Text.Encoding.UTF8.GetBytes("link[url]=" + url)
        req.ContentLength = buffer.Length

        Dim ios As System.IO.Stream = req.GetRequestStream()
        ios.Write(buffer, 0, buffer.Length)

        Try
            Dim reader As System.IO.StreamReader = _
                New System.IO.StreamReader(req.GetResponse().GetResponseStream())

            Dim retValue As String = reader.ReadLine()

            reader.Close()

            Return retValue
        Catch ex As WebException
            Return ex.Message
        End Try
    End Function

Notice that we have specified the POST method because it's required if you are going to change some data in the server. It's worth mentioning too that we have set the content type toapplication/x-www-form-urlencoded because it's required if you are going to push data to a web form (it's usually perfect for all web forms except file-uploads.)

In addition, we have included the input required in the request stream.

What's next

Some other articles about URL shortening services are available here.