August 2009 - Posts

The other day I came across a pretty cool project, Linq2Twitter, that basically implements a linq provider for consuming the Twitter REST Api.  This project is not only interesting because it provides an intuitive model for incorporating Twitter calls into any existing application, but also because it shows how to use the OAuth authentication mode that the Twitter Api supports.

As it is common with other linq providers, this library provides a root class “TwitterContext” for executing queries or calling other services in the API.

So you can do things like this,

var twitterCxt = new TwitterContext();

var tweets =

    from tweet in twitterCtx.Status

    where tweet.Type == StatusType.Friends

    select tweet;

tweets.ToList().ForEach(

    tweet => Console.WriteLine(

        "Friend: {0}\nTweet: {1}\n",

        tweet.User.Name,

        tweet.Text));

The example above shows some code to gets the status of all your friends.

Before using any of the services available in the API, you must first authenticate in Twitter using either basic authentication (The traditional way with username and password) or OAuth. The authentication mode is specified in the twitter context.

In case you decide to go with OAuth, it is very simple to use. You only need to provide the OAuth secret and key associated to an application that you previously registered in Twitter.

Console.Write("Consumer Key: ");

twitterCtx.ConsumerKey = Console.ReadLine();

Console.Write("Consumer Secret: ");

twitterCtx.ConsumerSecret = Console.ReadLine();

string link = twitterCtx.GetAuthorizationPageLink(false, false);

Console.WriteLine("Authorization Page Link: {0}\n", link);

Console.WriteLine("Next, you'll need to tell Twitter to authorize access. This program will not have access to your credentials, which is the benefit of OAuth.  Once you log into Twitter and give this program permission, come back to this console and press Enter to complete the authorization sequence.\n\nPress Enter now to continue.");

Console.ReadKey();

// launches browser so you can log in and give permissions

Process.Start(link);

Console.WriteLine("\nYou should see your browser navigate to Twitter, saying that your application wants to access your Twitter account. Once you've authorized this program, return to this console and press any key to execute the LINQ to Twitter code.");

Console.ReadKey();

var uri = new Uri(link);

NameValueCollection urlParams = HttpUtility.ParseQueryString(uri.Query);

string oAuthToken = urlParams["oauth_token"];

twitterCtx.RetrieveAccessToken(oAuthToken);

if (twitterCtx.AuthorizedViaOAuth)

OAuth requires a browser session so you can log into twitter and authorize the client application to get your data. This is not a problem if the client application is a web application, the authentication and authorization processes flow very natural. However, in the case of Windows or Console Application, a browser instance needs to be created, this is what the example above is doing in the line “Process.Start”. If you are already authenticated in twitter, you will see this page where you need to authorize the application that wants to get access to your data.

Twitter

It looks like Andrew Arnott have been involved in the OAuth implementation for this library, which is a really good thing since he is the main contributor in two of the most stables projects for OpenID (DotNetOpenId) and OAuth (DotNetOpenAuth) in the .NET world. 

Posted by cibrax | 1 comment(s)
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