Using FQL With Facebook C# SDK

The full meaning of FQL is ‘Facebook Query Language’. This is used to retrieve filtered data from Facebook API, similar to how an SQL query works with a database. You won’t find it exactly like SQL query syntax all the time, and not all kinds 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 assume you are familiar with using Facebook graph API through c#. If you are a beginner Facebook API developer in c#, you should better start with another article about getting started with Facebook graph API in c#. Also, you should be familiar with the FacebookSDK library so you can use the examples here. If not yes, please read another tutorial about getting started with facebooksdk/c#

Why FQL?

The simple answer is: For performance tuning, make API calls faster and get only the data that is needed(filters in the ways where general graph API can’t). Suppose you need some filtering while retrieving friends who meet certain criteria and also need only certain information; then FQL will perform better for you than a general API call. Because, with graph API calls, you will get a lot of information, and you will have to filter them on your end. So, the time between making the API call and getting the response will increase by a huge amount, especially 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, you won’t even be able to do any JOIN operations. You will have to find alternative ways to do this. Like, you can execute multiple queries on a single request. Also, you are required to use the ‘WHERE’ condition to filter 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 any table, you should see that one or more column(s) on every table are marked as ‘*’. Those columns are known as ‘Index-able’ columns. To use FQL, one of your prerequisites is to use any one(at least) or more indexable column(s) in the ‘WHERE’ condition.

Simple FQL Operation Syntax in C# FacebookSDK:

Here is a very simple FQL operation example using c#/FacebokSDK code, which will retrieve all your female friends of:(The code snippet is from a MVC web application, but you will get a clear idea of 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
    }
}Code language: JavaScript (javascript)

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 kinds of searching operations, then you will have to use ‘strpos’ method inside the FQL as follows:

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

The above FQL query will return to you all the friends who have the ‘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 the official Facebook documentation on FQL for details. Don’t hesitate to ask me if you have any questions. Happy coding 🙂