Using FQL With Facebook C# SDK

Full meaning of FQL is ‘Facebook Query Language’. This is used to retrieve filtered data from facebook api similarly as sql query works with database. You won’t find it exactly like SQL query syntax all the time, and not all kind of operations too. But, it definitely meets the demand. In this tutorial, i will try to explain using fql in your .NET application with c# code examples where applicable. I am assuming, you are familiar with using facebook graph api through c#. If you are a beginner Facebook api developer in c#, you should better start by another article about getting started with Facebook graph api in c#. Also, you should be familiar with facebooksdk library also to use the examples here. If not yes, please read another tutorial about getting started with facebooksdk/c#

Why FQL?

Simple answer is: for performance tuning, make api calls faster and get data only which are needed(filters in the ways where general graph api can’t). Suppose, if you need some filtering while retrieve friends which meets a certain criteria and also, need only certain information, then fql will perform better for you then general api call. Because, with graph api call, you will get a lot of information and you will have to filter them on your end. so, time between making the api call and get the response will increase in a huge amount, specially because of the amount of data to be transferred.

SQL Operations Supported By FQL:

You can only make select operations. Naturally, you won’t be able to make any insert/update/delete operations. Moreover, even you won’t be able to do any join operations too. You will have to find alternative ways for this. Like, you can execute multiple query on a single request. Also, its require that, you must using ‘WHERE’ condition for filtering results. otherwise it won’t work. Like, if you just want to retrieve all user’s all info, you aren’t gonna get the result, right?

Understanding index-able columns and their purposes:

If you look at the facebook documentation’s FQL section and enter to any table, you should see that, one or more column(s) on every tables are marked as ‘*’ . Those columns are known as ‘Index-able’ columns. To use FQL, one of your prerequisite is that you will have to use any one(at least) or more index-able column(s) in ‘WHERE’ condition.

Simple FQL Operation Syntax in C# FacebookSDK:

Here is a very simple fql operation example with using c#/faceboksdk code, which will retrieve all the female friends of yours:(code snippet is from a mvc web application, but you will get clear idea how to use the fql)

        //will return a facebook session object
        public FacebookSession FacebookSession
        {
            get { return (new CanvasAuthorizer().Session); }
        }

        public MyController()
        {
            try
            {
                //create a new instance of facebook app 
                var fbApp = new FacebookClient(this.FacebookSession.AccessToken);
          
                //basic graph api call to retrive user's information
                dynamic result = fbApp.Get("me");
                ViewData["Firstname"] = result.first_name;
                ViewData["Lastname"] = result.last_name;
                
                //basic fql query execution 
                dynamic friends = fbApp.Query("SELECT uid, name, pic_square FROM user WHERE uid IN (SELECT uid2 FROM friend WHERE uid1 = me()) AND sex='female'");
                
                //loop through all friends and get their name and create response containing friends' name and profile picture
                foreach( dynamic friend in friends )
                {
                   result += friend.name+"<img src='"+friend.pic_square+"' alt='"+friend.name+"' /><br />";
                }

            }
            catch
            { 
                //error handling code
            }
        }

Other Operators:

You can also use ‘Limit’ keyword in your FQL exactly in the same way as you did on SQL. However, there is no support for ‘Like’ keyword. If you want to use those kind of searching operations, then you will have to use ‘strpos’ method inside the fql like as follows:

SELECT uid, name, pic_square FROM user WHERE uid IN (SELECT uid2 FROM friend WHERE uid1 = me()) AND strpos(name,'abc')>=0

The above fql query will return you all the friends who have ‘abc’ keyword in their name.

Execute FQL Asynchronously:

You can also execute fql query asynchronously in c#. To achieve this, we just will have to use ‘QueryAsync’ method instead of ‘Query’ and pass extra parameter for the callback handler method.

References:

Hope this small fql tutorial is helpful on the way of your facebook application development. Please visit official facebook documentation on fql for details. Don’t hesitate to ask me if you have any questions. Happy coding 🙂