This policy has been enforced to prevent session riding, for further details look this Karen Corby’s blog post on cross domain requests.

Turns out that in silverlight, HTTP requests to non-original domains are allowed if the server has exclusively allowed to accept requests. The primary way of enabling cross domain calls is through a policy file placed at the root of the server.  Two types of policy files are supported:

1. Silverlight Cross Domain Policy File (clientaccesspolicy.xml)
2. (A subset of the) Flash Cross Domain Policy File (crossdomain.xml)

Now, the problem is that twitter don’t have policy files placed in the server root. Possible way to get around this is to use a proxy for requests. you can make a proxy on your server, that can on application request, fetch the RSS data from twitter and send it back to your application. EASY!

but what if, you don’t want your own server proxy…

reasons:

• you will have to add a policy file to your server root
• that will cause increase in the server bandwidth usage and server stress
• it’s hell lot of work

simple! use Yahoo Pipes, why?

• Its easy
• because, they allow you to request RSS feeds from other sites (multiple sites in one request)
• they have cross-domain policy files placed on there server roots, that means your silverlight application will be able to fetch the Twitter data via a yahoo pipe

What is a yahoo pipe?

Content-source: http://pipes.yahoo.com/pipes/

Pipes is a powerful composition tool to aggregate, manipulate, and mashup content from around the web.

Like Unix pipes, simple commands can be combined together to create output that meets your needs:

• combine many feeds into one, then sort, filter and translate it.
• geocode your favorite feeds and browse the items on an interactive map.
• power widgets/badges on your web site.
• grab the output of any Pipes as RSS, JSON, KML, and other formats.

simply speaking, a yahoo pipe is url like this:

http://pipes.yahooapis.com/pipes/pipe.info?_id=bas782j290jq9dd2nmaklfhj93ji9d3j

you design its behaviour on a design surface

So, a yahoo pipe can be designed to take single/multiple feed URLs, fetch the feeds and provide an aggregated feed which can be consumed by your silverlight application under cross domain policy.

further, you can provide test data and see results right there.

Run it and get the aggregated RSS URL from the run screen.

The pipe, I used looks like this

http://pipes.yahooapis.com/pipes/pipe.run?_id=f0cf1b0851bd8243dbf8bd63c07b8d11&_render=rss&feedUrl=<some_feed_url>

Now fetching the data in your silverlight application is damn easy…

private string proxy = "http://pipes.yahooapis.com/pipes/pipe.run?_id=f0cf1b0851bd8243dbf8bd63c07b8d11&_render=rss&feedUrl=";
private string feedUrl = "http://twitter.com/statuses/user_timeline/22100709.rss";
void DownloadFeed()
{
            string url = proxy + feedUrl;
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
            request.Method = "GET";
            request.BeginGetResponse(new AsyncCallback(ResponseHandler), request);
}
void ResponseHandler(IAsyncResult asyncResult)
{
            try
            {
                HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
                HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult);
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    Stream stream = response.GetResponseStream();
                    int len = 1024;
                    byte[] buf = new byte[len];
                    int read = 0;
                    xml = "";
                    do
                    {
                        read = stream.Read(buf, 0, len);
                        xml += Encoding.UTF8.GetString(buf, 0, read);
                    }while (read > 0);
                    stream.Close();
                    ParseRSSFeed(xml);
                }
            }
            catch (System.Security.SecurityException ex)
            {
                // Do Something
            }
 }

Next, you can include Linq to Xml (add System.Xml.Linq to References) to easily and quickly parse the xml to fetch the user tweets. 

You can read more about that on Scott Gu's blog post: Silverlight Tutorial Part 3: Using Networking to Retrieve Data and Populate a DataGrid

Here is, how I have done it:

The feed  you get from twitter will look like this:

<?xml version="1.0" encoding="utf-16"?>
<rss xmlns:atom="http://www.w3.org/2005/Atom" version="2.0">
    <channel>
        <title>Twitter / LON3WOLF</title>
        <link>http://twitter.com/LON3WOLF</link>
        <atom:link type="application/rss+xml" href="http://twitter.com/statuses/user_timeline/22100709.rss" rel="self" />
        <description>Twitter updates from Sanil Singh Tomar / LON3WOLF.</description>
        <language>en-us</language>
        <ttl>40</ttl>
           <title>LON3WOLF: ehem... RT @Zee: awww man...RT @patrick Best toilet ever! http://twitpic.com/rcvp2 #fb</title>
        <item>
            <title>LON3WOLF: @anilbpai you mean one that looks like xkcd, if you find any tool 4 that, then please RT  </title>
            <description>LON3WOLF: @anilbpai you mean one that looks like xkcd</description>
            <pubDate>Sat, 28 Nov 2009 16:40:22 +0000</pubDate>
            <guid>http://twitter.com/LON3WOLF/statuses/6144843401</guid>
            <link>http://twitter.com/LON3WOLF/statuses/6144843401</link>
        </item>
        <item>
            <title>LON3WOLF: @anilbpai Go to ' Block ' button-&amp;gt; Click! Click!  </title>
            <description>LON3WOLF: @anilbpai Go to ' Block ' button-&amp;gt; Click! Click!  </description>
            <pubDate>Fri, 27 Nov 2009 18:38:03 +0000</pubDate>
            <guid>http://twitter.com/LON3WOLF/statuses/6119125496</guid>
            <link>http://twitter.com/LON3WOLF/statuses/6119125496</link>
        </item>
    </channel>
</rss>

You can use Linq to XML in following way:

public class item
{
        public string title;
        public string description;
        public string pubDate;
        public string guid;
        public string link;
}
public void ParseRSSFeed(string xmlContent)
 {
            XDocument rss = XDocument.Parse(xmlContent);
            var tweets = from feed in rss.Descendants("channel").Descendants("item")
                        select new item
                        {
                            guid = (string) feed.Element("guid"),
                            pubDate = (string)feed.Element("pubDate"),
                            title = (string)feed.Element("title"),
                            description = (string)feed.Element("description"),
                            link = (string)feed.Element("link")
                        };
            Status = new item[tweets.Count()];
            //Copy description to status
            int count = 0;
            foreach (var tweet in tweets)
            {
                Status[count] = tweet;
                count++;
            }
 }

Links:

Source Code: Download

Application: Download

This policy has been enforced to prevent session riding, for further details look this Karen Corby’s blog post on cross domain requests.

Turns out that in silverlight, HTTP requests to non-original domains are allowed if the server has exclusively allowed to accept requests. The primary way of enabling cross domain calls is through a policy file placed at the root of the server.  Two types of policy files are supported:

1. Silverlight Cross Domain Policy File (clientaccesspolicy.xml)
2. (A subset of the) Flash Cross Domain Policy File (crossdomain.xml)

Now, the problem is that twitter don’t have policy files placed in the server root. Possible way to get around this is to use a proxy for requests. you can make a proxy on your server, that can on application request, fetch the RSS data from twitter and send it back to your application. EASY!

but what if, you don’t want your own server proxy…

reasons:

• you will have to add a policy file to your server root
• that will cause increase in the server bandwidth usage and server stress
• it’s hell lot of work

simple! use Yahoo Pipes, why?

• Its easy
• because, they allow you to request RSS feeds from other sites (multiple sites in one request)
• they have cross-domain policy files placed on there server roots, that means your silverlight application will be able to fetch the Twitter data via a yahoo pipe

What is a yahoo pipe?

Content-source: http://pipes.yahoo.com/pipes/

Pipes is a powerful composition tool to aggregate, manipulate, and mashup content from around the web.

Like Unix pipes, simple commands can be combined together to create output that meets your needs:

• combine many feeds into one, then sort, filter and translate it.
• geocode your favorite feeds and browse the items on an interactive map.
• power widgets/badges on your web site.
• grab the output of any Pipes as RSS, JSON, KML, and other formats.

simply speaking, a yahoo pipe is url like this:

http://pipes.yahooapis.com/pipes/pipe.info?_id=bas782j290jq9dd2nmaklfhj93ji9d3j

you design its behaviour on a design surface

So, a yahoo pipe can be designed to take single/multiple feed URLs, fetch the feeds and provide an aggregated feed which can be consumed by your silverlight application under cross domain policy.

further, you can provide test data and see results right there.

Run it and get the aggregated RSS URL from the run screen.

The pipe, I used looks like this

http://pipes.yahooapis.com/pipes/pipe.run?_id=f0cf1b0851bd8243dbf8bd63c07b8d11&_render=rss&feedUrl=<some_feed_url>

Now fetching the data in your silverlight application is damn easy…

private string proxy = "http://pipes.yahooapis.com/pipes/pipe.run?_id=f0cf1b0851bd8243dbf8bd63c07b8d11&_render=rss&feedUrl=";
private string feedUrl = "http://twitter.com/statuses/user_timeline/22100709.rss";
void DownloadFeed()
{
            string url = proxy + feedUrl;
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
            request.Method = "GET";
            request.BeginGetResponse(new AsyncCallback(ResponseHandler), request);
}
void ResponseHandler(IAsyncResult asyncResult)
{
            try
            {
                HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
                HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult);
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    Stream stream = response.GetResponseStream();
                    int len = 1024;
                    byte[] buf = new byte[len];
                    int read = 0;
                    xml = "";
                    do
                    {
                        read = stream.Read(buf, 0, len);
                        xml += Encoding.UTF8.GetString(buf, 0, read);
                    }while (read > 0);
                    stream.Close();
                    ParseRSSFeed(xml);
                }
            }
            catch (System.Security.SecurityException ex)
            {
                // Do Something
            }
 }

Next, you can include Linq to Xml (add System.Xml.Linq to References) to easily and quickly parse the xml to fetch the user tweets. 

You can read more about that on Scott Gu's blog post: Silverlight Tutorial Part 3: Using Networking to Retrieve Data and Populate a DataGrid

Here is, how I have done it:

The feed  you get from twitter will look like this:

<?xml version="1.0" encoding="utf-16"?>
<rss xmlns:atom="http://www.w3.org/2005/Atom" version="2.0">
    <channel>
        <title>Twitter / LON3WOLF</title>
        <link>http://twitter.com/LON3WOLF</link>
        <atom:link type="application/rss+xml" href="http://twitter.com/statuses/user_timeline/22100709.rss" rel="self" />
        <description>Twitter updates from Sanil Singh Tomar / LON3WOLF.</description>
        <language>en-us</language>
        <ttl>40</ttl>
           <title>LON3WOLF: ehem... RT @Zee: awww man...RT @patrick Best toilet ever! http://twitpic.com/rcvp2 #fb</title>
        <item>
            <title>LON3WOLF: @anilbpai you mean one that looks like xkcd, if you find any tool 4 that, then please RT  </title>
            <description>LON3WOLF: @anilbpai you mean one that looks like xkcd</description>
            <pubDate>Sat, 28 Nov 2009 16:40:22 +0000</pubDate>
            <guid>http://twitter.com/LON3WOLF/statuses/6144843401</guid>
            <link>http://twitter.com/LON3WOLF/statuses/6144843401</link>
        </item>
        <item>
            <title>LON3WOLF: @anilbpai Go to ' Block ' button-&amp;gt; Click! Click!  </title>
            <description>LON3WOLF: @anilbpai Go to ' Block ' button-&amp;gt; Click! Click!  </description>
            <pubDate>Fri, 27 Nov 2009 18:38:03 +0000</pubDate>
            <guid>http://twitter.com/LON3WOLF/statuses/6119125496</guid>
            <link>http://twitter.com/LON3WOLF/statuses/6119125496</link>
        </item>
    </channel>
</rss>

You can use Linq to XML in following way:

public class item
{
        public string title;
        public string description;
        public string pubDate;
        public string guid;
        public string link;
}
public void ParseRSSFeed(string xmlContent)
 {
            XDocument rss = XDocument.Parse(xmlContent);
            var tweets = from feed in rss.Descendants("channel").Descendants("item")
                        select new item
                        {
                            guid = (string) feed.Element("guid"),
                            pubDate = (string)feed.Element("pubDate"),
                            title = (string)feed.Element("title"),
                            description = (string)feed.Element("description"),
                            link = (string)feed.Element("link")
                        };
            Status = new item[tweets.Count()];
            //Copy description to status
            int count = 0;
            foreach (var tweet in tweets)
            {
                Status[count] = tweet;
                count++;
            }
 }

Links:

Source Code: Download

Application: Download

Presenting Code Garage

We all (The Programmers) write handy tools and other hell things that can make our life easier (or harder). We don’t mind it sharing it with others. They are tiny apps/utilities created just for fun or some serious job, made in free time when some idea strikes you.

With the idea of sharing those utilities and source code, here I am presenting Code Garage. Here you can download the applications or use the Source Code, in a way you want.

License??

Oh! yes it does comes with a license, its WTFPL.

What is that??

WTFPL : Do What The Fuck You Want Public License. (here is original link )

Seriously, What’s that?

Well, here is how it  binds you:

  DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004
 Copyright (C) 2004 Sam Hocevar
  14 rue de Plaisance, 75014 Paris, France
 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.
            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
  0. You just DO WHAT THE FUCK YOU WANT TO.

In Summary: You can do whatever you want, you are FREE!

Q: Can I do that?

A: yes, you can

Q: And that?

A: duh! Yes

Q: Can I add my code here?

A: Yes you can, though I would like to see an entire your own blog dedicated to that. but, still if you want you are welcome, just send me an email

Last Word: I hold no liabilities, if you happen to use any code/utilities from here and something bad happens to you, including any loss incurred in any form. That means I am free too from any liabilities, you can’t sue me in anyway.

Said that, here is a list of the utilities/source code etc that I have uploaded and published plus those that I plan to upload:

• SMTP
• Alarm
• Processviewer
• BookStore
• CDStore
• VinkrIt gadget
• BSoD
• A-Z
• Search Plugin
• DNS Query
• Desktop Shock
• batch & Regs
• Desktop Draw
• Chronometer
• Search Gadget
• Pagination Extension
• Crazy drive
• MOaB
• Keyboard logger
• xKernel
• TCP Socket demo for unix
• basic java car anim
• Expense Reporter

Yeah! it covers lamest things, I happen to write.

Still have questions?

Side Note: I am big fan of that blog, its awesome and enlightening

Well, here is an excerpt of that post:

Check out the code below:

using System.Linq;
class Program
{
  static void Main()
  { 
      int[] data = { 1, 2, 3, 1, 2, 1 };
      foreach (var m in from m in data orderby m select m)
            System.Console.Write(m);
  }
}

Now, the question is:

  Is this code valid or not??

  If valid, how?

  If not valid, why?

(Source: Eric Lippert’s Blog) 

So, I worked on that problem posted some comments there, and presenting it again here in the form of a post.

The moment I read the problem, things started running in my mind around

var m in from m in data orderby m select m

as you can perceive, m is being used in two different contexts, first as a enumerator in LINQ query: " from m in data orderby m select m "

and the "var m " part in foreach. The question here: Can that possibly work?

Luckily, I was honing my skills in Reflection (System.Reflection) at that time, I get across a phrase in this book about foreach block (it says Cs compiler adds some temp. variable to smooth out operations like

a += 2;

or

foreach(var m in M){}

along with that there was also a prenotion that something "magical" happens when you encounter such situation, and whole code behaves like it is working in scopes (The blocks of { }).

So, the possible explanation, that came to my mind about this problem was :

the thing "var m in from m in data orderby m select m"

breaks up into two scopes : { var m } in { from m in data orderby m select m }

or in other terms var m in {from m in data orderby m select m}

We can proceed to further abstractions

var m = {from m’ in data order by m’ select m’}

that would eventually looks like

var m in m’ // where m’ is enumerable

[ Oops, m' is not a valid name for a variable, but good for human beings]

OK! I have a possible explanation, now how to confirm that its right and not a conjecture.

I fired RSS Bandit and rushed to Eric Lippert’s blog…

<digression>

x-(

Though I like reading blogs, but Internet, blogs and twitter (a.k.a Knowledge Supernova) provide so much information to absorb, I occasionally procrastinate reading RSS and let them aggregate scheduled to be read on weekends, after I am exhausted  from celebrating TGIF and TGIS, so I missed the Eric Lipperts blog post that mentioned this problem

</digression>

I fired RSS Bandit and rushed to Eric Lippert’s blog and tried to find out where this problem is being discussed, and I failed to figure its occurrence since it was phrased at the end of blog post and I was flipping over top.

This made me more curious to find the real answer, so I fired VS, hit Ctrl + C, Ctrl+ V and some tabs, ran it and yes it was running fine, just like you would expect.

But, that doesn’t answer actually what concerns me: Is my explanation is completely right?

Suddenly, an idea struck me: Utilize Reflection

Advantage was that, it will cause extra practice much needed to get comfortable with reflection

So, I started writing code:

First, I wrote

using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Collections.Generic;
    class Program
    {
      static void Main()
      {
         int[] data = { 1, 2, 3, 1, 2, 1 };
          foreach (var m in from m in data orderby m select m)
             System.Console.Write(m);
          new Analyse().Run();
          System.Console.ReadKey();
      }
    }
    class Analyse
    {
        public void Run()
        {
            Assembly asm = Assembly.GetAssembly(typeof(Program));
            MethodBody mb = asm.EntryPoint.GetMethodBody();
            System.Console.WriteLine("\nMethod Name: "+asm.EntryPoint.Name);
            foreach (var locals in mb.LocalVariables)
            {
                System.Console.WriteLine("\n {0}", locals.LocalType.FullName);
            }
            System.Console.ReadKey();
        }
    }

The Run method would actually list all the variables that are present after actual compilation, this will include the variables we have declared explicitly or implicitly as well as other variables introduced by compiler to store temporary results and perform calculations.

If you run it you will get output:

 

111223

Method Name: Main

System.Int32[]

System.Int32

System.Collections.Generic.IEnumerator`1[[System.Int32, mscorlib, Version=2.0.0.

0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

System.Boolean

Ok! Let me set a context, before I go for explaining things here

change the body of main() method inside program class to

using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Collections.Generic;
    class Program
    {
      static void Main()
      {
         int[] data = { 1, 2, 3, 1, 2, 1 };
          foreach (var num in data)
          {
              System.Console.Write(num);
          }
          new Analyse().Run();
          System.Console.ReadKey();
      }
    }
... contd.

How the output changes:

123121

Method Name: Main

System.Int32[]

System.Int32

System.Int32[]

System.Int32

System.Boolean

A little explanation

the first system.Int32[] is this array int[ ] data = { 1, 2, 3, 1, 2, 1 };

next System.Int32 will receive value at each iteration and will be used in Write() [this is our var m]

the second System.Int32[] refers to ForEach’s copy of array. Remember foreach doesn’t allow changing contents, so it makes a copy.

the second Int32 is an index to track current iterator location

last is a boolean which stores the result of condition check

Note: this is again guess work, but still quiet predictable

Note that there are two occurrence of System.Int32, than how can I figure out, what is the purpose of the second one and last one

so, we again change the main() body to

static void Main()
      {
         char[] ch = { 'a', 'b', 'c' };
         foreach (var num in ch)
         {
             System.Console.Write(num);
         }
          new Analyse().Run();
          System.Console.ReadKey();
      }
...
..

the output changes to :

abc

Method Name: Main

System.Char[]

System.Char

System.Char[]

System.Int32

System.Boolean

so, you can see that, system.char (replacing first System.Int32) is getting the assigned value that will be Write() outputted, and thus by comparing the ordinal similarity between the two outputs, it would be right to think that first System.Int32 is receiving the current value of data (index to which, iteration is pointing).

Back to our actual code, analysing the output

111223

Method Name: Main

System.Int32[]

System.Int32

System.Collections.Generic.IEnumerator`1[[System.Int32, mscorlib, Version=2.0.0.

0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

System.Boolean

line by line, we can see that

System.Int32[ ]

(the actual data[] array)

System.Int32

(that will receive value at each iteration and will be WriteLined/outputted)

System.Collections.Generic.IEnumerator`1[[System.Int32, mscorlib blah blah blah... ]]

( the generic IEnumerator generated from LINQ expression obtained, now all classes implementing IEnumerator has a method called MoveNext( ), hence it will not require any additional Sytem.int32 indexer, hence here it is absent in output)

System.Boolean

(condition check result as previously stated)

From all this, we get that compiler handle duplicate references smartly, until we play by his rules and work according to C# language specs

This technique forms (No, I didn’t discovered it) another tool to analyse the code behaviour.

As a side note, other such techniques you are familiar with are:

• looking at preprocessor output (those *.i files in C)
• looking at post compile code
• Looking at generated assembly code
• running ILDASM x-(
• debugging??
• blah blah blah (ask a real Expert, he will provide you an exhaustive list of such techniques)

THE HAPPY ENDING

finally, on the other day when I was reading posts aggregated in RSS Bandit from coding horror, many other blogs and somewhere in middle Eric’s blog, I find this problem hiding at the bottom of the blog post, and by reading the blog post you can get the explanation and It seems that, I stand correct Still if you think, I am wrong somewhere, please comment here. I will be happy to get the right facts.

Edit: I just found out that, Eric also posted next post in continuation to that problem, where he explains excellently the behaviour of this code, in his own way.

In spite of being useless apps, multitude of people are rushing towards such apps…

don’t believe me! Have  a look on stats of an application (A “who” quiz) that I launched,  four days ago:

but, look writing these applications are pretty straight right, and further with facebook platform API support, it becomes a breeze, though it adds its own idiosyncrasies and difficulties. And with all that things comes an easy way to make money by showing ads, and other revenue models that  can offer you considerable amount of money.

Getting Started

Add facebook developer application

To start with, every developer who wants to develop facebook applications need to add “facebook developer application“. [ Here, I assume you already have a valid facebook user account ]

A WebServer / web space running required middleware language

Next you will need a web space (host) to host your application. A facebook application is basically a web application that communicates with facebook platform with its REST APIs.

These REST APIs functionality are available in the form of libraries for different platforms, that allows you to use facebook API without writing a lot of extra code. facebook has created there own PHP client library.

Other than that, there  are plenty of unofficial libraries for supporting application development in your preferred language or framework.

I will be demonstrating here app development using the default PHP facebook API client library.

Facebook Application Architecture

Facebook provides your application to users when they request it through Facebook Application directory or follow some link pointing to your application. As you can see above, each time a Facebook user interacts with your application, It causes a series of server interactions with the Facebook server farm and your server. Each time a user requests something from your application  through Facebook,  that request is passed to your server to create the initial REST call to the Facebook API. Once your response to construct a display call (in FBML and HTML) and passes that back to the Facebook server. Facebook processes  this information (the embedded FBML and JS) and creates an HTML response to the user. Because of the constant passing of information between servers,  there  is an additional level of complexity that can complicate tracking down bugs. You also need to consider this constant interaction when developing your application because you don’t want to make unnecessary API calls that will slow down your application.

Download Client-Library

As discussed earlier, you can choose one from many available client libraries available for your favourite language. We will be using official facebook PHP Client Library, for other languages you can get one from unofficial libraries.

Once you’ve downloaded the library unzip it into a folder and upload to your webserver from where it is accessible by your PHP scripts. So you would have something like /php_include_directory/facebook/ and in that folder you will have the entire Facebook PHP Client Library (folders: client, footprints, php4client). I’m using PHP5 so my examples will be using the “client” directory of the library. The client library contains files and folders shown below:

Create Your Application Profile And API Key

go here, and create an application profile

Choose a name for your application. This is important because it’s what users will see when they are browsing the application directory. Currently the name field is the only thing used when searching for applications. So it’s doubly important at this point.

Next fill out the Canvas Callback Url with the location of your script. This is the public URL on your webserver where the Facebook application will be, also fill out the “Canvas Page URL”. This is your application URL within Facebook. For example if the application was called “Play the DemoApp ” then the application URL could be: “DemoApp” which would make the full URL: http://apps.facebook.com/DemoApp/.

All of these settings can be changed anytime, even after the application has been created 

Get the API Key and Secret

You should never disclose the API Secret key (Hmm… Isn’t that what secret means?), the API key is used to uniquely identify your application and Secret is used for authentication purpose and during REST API calls.

So far, we have selected a webserver that supports your chosen middleware language (in our case PHP), now we can start writing our application.

Select your IDE

You can write your PHP applications on any suitable editor, even on notepad but that hearts a bit, so you can choose some common free or proprietary IDEs from here on wikipedia, further in addition below is a list of some common IDEs:

• Crimson (http://www.crimsoneditor.com/)  [Windows]
• ConTEXT (http://www.context.cx/)  [Windows]
• Dreamweaver (http://www.adobe.com/products/dreamweaver/)  [Windows, OS X]
• Eclipse PDT (http://www.eclipse.org/pdt/)  [Windows, OS X, *nix]
• EditPad Lite (http://www.editpadpro.com/editpadlite.html)  [Windows]
• Notepad++ (http://notepad-plus.sourceforge.net/uk/site.htm)  [Windows]
• phpDesigner (http://www.mpsoftware.dk/)  [Windows]
• PhpEd (http://www.nusphere.com/products/phped.htm)  [Windows]
• PhpEdit (http://www.waterproof.fr/)  [Windows]
• PHP Expert Editor (http://www.ankord.com/phpxedit.html)  [Windows]
• Quanta Plus (http://quanta.kdewebdev.org/)  [*nix]
• TextMate (http://macromates.com/)  [OS X]

So, lets make our Demo App, what it will do:

• It will ask for user authorization to allow fetching user information via APIs
• List some information about user

    <?php
        // Name: index.php
        // My Demo App
        // facebook API library
        require_once '../facebook-platform/php/facebook.php';
        // The API key + secret
        $api_key = "546dcaef3d4c5666c5eef65c4c15e196";
        $secret = "57secret57secret57secret57secret";
        // Create the object containing API Client
        $facebook = new Facebook($api_key, $secret);
        // Shows standard "allow application" dialog, if user has not authorized
        $user_id = $facebook->require_login();
    ?>
    <?php
        // all API calls of form xxxx.function are called in the way xxxx_funtion in PHP API Client
        // call the users.getInfo facebook API
        // more details at http://wiki.developers.facebook.com/index.php/Users.getInfo
        $userdetails = $facebook->api_client->users_getInfo($user_id,'name,pic,profile_url');
        echo "<h2> Demo App </h2>";
        echo "<img src='".$userdetails[0]['pic']."' />";
        echo "<br />Name:".$userdetails[0]['name'];
        echo "<br /><a href='".$userdetails[0]['profile_url']."' >Go to profile</a>";
    ?>

Save it as index.php and upload it under proper directory at your server, so that references to php client library are correct.Next, launch your browser, and type your application facebook application canvas url, it would be like: http://apps.facebook.com/<app-name>When you will run it, you will see the following screen:

This screen is a result of our following line of code

$user_id = $facebook->require_login();

which causes facebook to show a standard prompt, through which our application gets permission to fetch user info from facebook profile datastore via API calls.

Click Allow to continue using app.

next we issue another API call:

$userdetails = $facebook->api_client->users_getInfo

This causes the REST API calls, and finally $userdetails contains the following value as an array:

which  we later print out using echo in out format:

It is to be noted that all facebook applications run on the facebook page and thus are allowed a fixed space called application canvas, the blue box marks the facebook canvas in snapshot below:

(Click to enlarge)

Where to go from here:

What you have learned here are bare basics of FB App platform, for further information you can see following places:

You can start playing with APIs without any need of coding by going to developer tools.

Resources and Further Reading

• Facebook Developers Site
• Facebook Developers Wiki
• Developing with the Facebook Platform and PHP
• Basic Facebook Application Architecture
• How URLs Are Handled Within An Application
• Understanding Your Callback Page

Book: Apress Facebook API Developers Guide (Mar 2008)

Forums: Facebook Forums

Hope you like this post providing some insight of facebook application development, please comment your views and post any queries freely.

Thanks for reading!

The aim of this extension is to make it simpler to navigate between different blog posts quickly.

It also have some little customisability by editing its CSS from extension manager to customize the look of the buttons. You can also change the maximuum number of buttons from the extension manager.

This has all been thrown together rather quickly so apologies for any problems you encounter. 

Please send any feedback/bug reports to me and I will try and correct asap.

Thanks.

Download [ Pagination.zip ]

Installation Instructions:

Just unzip the compressed zip archive and copy/upload the Pagination.cs file to your BlogEngine.NET extension folder.

Path relative to BlogEngine root:  /AppCode/Extensions/

The method is very simple and you can use without any hassles. Needless to say that your motherboard should support USB Boot feature to make use of the bootable USB drive.

1. Requirements

• USB Flash Drive (> 4GB)
• Windows 7 or Vista installation disk

2. Method

Plug-in your USB flash drive to USB port and move all the contents from USB drive to a safe location on your system.

Open Command Prompt with admin rights. Use any of the below methods to open Command Prompt with admin rights.

*Type cmd in Start menu search box and hit Ctrl+ Shift+ Enter.

Or

*Go to Start menu > All programs > Accessories, right click on Command Prompt and select Run as administrator.

3. You need to know about the USB drive a little bit. Type in the following commands in the command prompt:

First type DISKPART and hit enter to see the below message.

Next type LIST DISK command and note down the Disk number (ex: Disk 1) of your USB flash drive. In the below screenshot my Flash Drive Disk no is Disk 1.

Now proceed further on path1 or path2 as the condition may be true.

Path 1: Here I assume that your disk drive no is “Disk 1″ and it is a pen drive with capacity > 4 GB and no partition having your important data

Type all the below commands one by one.

Note: If you have Disk 2 as your USB flash drive then use Disk 2.

Refer the above step to confirm it.

So below are the commands you need to type and execute one by one:

SELECT DISK 1

CLEAN

CREATE PARTITION PRIMARY

SELECT PARTITION 1

ACTIVE

FORMAT FS=NTFS

(Format process may take few seconds)

ASSIGN

EXIT

————————–

Path2: If you have a big USB Disk/ External Disk/ Portable hard disk, you can create a primary partition in it using disk manager and skip the CLEAN command, thus you don’t loose your data stored on other partition of same disk. Lets see how…

If you have a big USB disk, proceed by typing following command

SELECT DISK 1

LIST PARTITION

SELECT PARTITION 2

Partition 2 is a 10 GB partition created for installation purpose.

ACTIVE

FORMAT FS=NTFS

(Format process may take few seconds)

ASSIGN

EXIT

after going through path1 /path2, next insert your Windows7/Vista DVD into the optical drive and check the drive letter of the DVD drive. In this guide I will assume that your DVD drive letter is “D” and USB drive letter is “H” (open my computer to know about it).

4. Maximize the minimized Command Prompt in the 4th step.Type  the following command now:

D:CD BOOT and hit enter.Where “D” is your DVD drive letter.

CD BOOT and hit enter

5. Next, Copy your Windows 7/Vista DVD contents directly to the USB flash drive.

6. Your USB drive is ready to boot and install Windows 7/Vista. Only thing you need to change the boot priority at the BIOS to USB from the HDD or CD ROM drive. I won’t explain it as it’s just the matter the changing the boot priority or enabling the USB boot option in the BIOS.

Note: If you are not able to boot after following this guide means you haven’t set the BIOS priority to USB. If you got any problem in following this guide feel free to ask questions by leaving comment.

Ok! The thing is that TwitPic API is not that much complex, since all TwitPic provides is that it lets you post your funny/sad looking pictures or any picture you want to post on it, so it can be shared on twitter or any other site. Its pretty much easy to implement all you have to know is how to create a web request, parse a XML, and post Multipart/form-data. You can get complete reference to TwitPic API here: http://twitpic.com/api.do

Since, hosting pictures is a part of some web applications that, I write and will write in future. So, I wrote my own library in .NET framework, that I can use to post pictures on TwitPic. As usual being a lazy guy and considering that code and methods involved are straight forward. I’m giving link to the CodePlex hosted project page, where you can download the library and complete source code (MS-Pl Licensed).

I have documented code at many places, wherever I thought was needed. So, there is very small possibility that you would say the “Holy F Word” while going through it, still if you may want to say so.

CodePlex Project Link http://twipli.codeplex.com

Here I would share the basic process, you need to follow to post your image file on TwitPic.com

TwitPic.com provides 2 methods: UploadAndPost and Upload

——————————————————————————————————————————–

METHOD: UploadAndPost

http://twitpic.com/api/uploadAndPost

Use this method to upload an image to TwitPic and to send it as a status update to Twitter.

——————————————————————————————————————————–

METHOD: Upload

http://twitpic.com/api/upload

Use this method if you just want to upload a photo to TwitPic.

——————————————————————————————————————————–

response to both method is in XML format.

Here is an example:

Fields to post in Method: UploadAndPost
(post data should be formatted as multipart/form-data):

- media (required) – Binary image data
- username (required) – Twitter username
- password (required) – Twitter password
- message (optional) – Message to post to twitter. The URL of the image is automatically added.

Response XML:

<?xml version="1.0" encoding="UTF-8"?>
<rsp status="ok"> <statusid>1111</statusid>
<userid>11111</userid>
<mediaid>abc123</mediaid>
<mediaurl>http://twitpic.com/abc123</mediaurl>
</rsp>

Here is the abstract sequence in C# that is needed to do above:

Let the variable Username and Password store the Twitter account credentials and ImagePath and Message are the path to image and Message to be posted.

The first step would be to prepare the post data in Multipart/form-data format

string boundary = Guid.NewGuid().ToString();
string requestUrl = "http://twitpic.com/api/uploadAndPost";
string encoding = "iso-8859-1";
string header = string.Format("--{0}", boundary);
string footer = string.Format("--{0}--", boundary);
StringBuilder contents = new StringBuilder();
contents.AppendLine(header);
//Add image to POST content string
 //determing file content-type                
string fileContentType = GetFileContentType(filename); //MIME type of image //The filename of image
string fileHeader =
String.Format("Content-Disposition: file; name=\"{0}\"; filename=\"{1}\"", "media", filename);
string fileData = Encoding.GetEncoding(encoding).GetString(binaryImageData);
contents.AppendLine(fileHeader);
contents.AppendLine(String.Format("Content-Type: {0}", fileContentType));
contents.AppendLine();
contents.AppendLine(fileData);
 //Add user field in POST string                  
contents.AppendLine(header);
contents.AppendLine(String.Format("Content-Disposition: form-data; name=\"{0}\"", "username"));
contents.AppendLine();
contents.AppendLine(Username);
//Add Password in POST string                 
contents.AppendLine(header);
contents.AppendLine(String.Format("Content-Disposition: form-data; name=\"{0}\"", "password"));
contents.AppendLine();
contents.AppendLine(Password);
 //Add Message in Post string                
if (!String.IsNullOrEmpty(Message))
{
                    contents.AppendLine(header);
                    contents.AppendLine(String.Format("Content-Disposition: form-data; name=\"{0}\"", "message"));
                    contents.AppendLine();
                    contents.AppendLine(Message);
}
contents.AppendLine(footer);
encoding = "iso-8859-1";
byte[] bytes = Encoding.GetEncoding(encoding).GetBytes(contents.ToString());

Here is the details of Method: GetFileContentType

It simply returns appropriate MIME type, for an image format.

private string GetFileContentType(string FileName)
        {
            if(FileName.EndsWith("jpg",true,System.Globalization.CultureInfo.CurrentCulture))
            {
                return "image/jpeg";
            }
            else if(FileName.EndsWith("jpeg",true,System.Globalization.CultureInfo.CurrentCulture))
            {
                return "image/jpeg";
            }
            else if(FileName.EndsWith("gif",true,System.Globalization.CultureInfo.CurrentCulture))
            {
                return "image/gif";
            }
            else if(FileName.EndsWith("png",true,System.Globalization.CultureInfo.CurrentCulture))
            {
                return "image/png";
            }
            else
            {
                return "";
            }
        }

Finally parse the response XML, this is done by METHOD: RSPXMLParser

private Response RSPXMLParser(string XMLresponse)
        {
            XmlDocument XmlDoc = new XmlDocument();
            int  UserId;
            int StatusId;
            string MediaId;
            string MediaUrl;
            int ErrorCode;
            string ErrorMessage;
            try
            {
                XmlDoc.LoadXml(XMLresponse);
                XmlNodeList RootNode = XmlDoc.SelectNodes("rsp");
                if(RootNode.Item(0).Attributes["status"].InnerText=="ok")
                {
                    MediaId = RootNode.Item(0).SelectNodes("mediaid").Item(0).InnerText;
                    MediaUrl = RootNode.Item(0).SelectNodes("mediaurl").Item(0).InnerText;
                    try
                    {
                        UserId = int.Parse(RootNode.Item(0).SelectNodes("userid").Item(0).InnerText);
                        StatusId = int.Parse(RootNode.Item(0).SelectNodes("statusid").Item(0).InnerText);
                        return new Response(StatusId, UserId, MediaId, MediaUrl);
                    }
                    catch
                    {
                        return new Response(MediaId, MediaUrl);
                    }
                }
                else
                {
                    //<err code="1001" msg="Invalid twitter username or password" />
                    ErrorCode = int.Parse(RootNode.Item(0).SelectNodes("err").Item(0).Attributes["code"].InnerText);
                    ErrorMessage = RootNode.Item(0).SelectNodes("err").Item(0).Attributes["msg"].InnerText;
                    return new Response(ErrorCode, ErrorMessage);
                }
            }
            catch(Exception ex)
            {
                return new Response("XML Parse error: "+ex.ToString());
            }
        }

The Response object referred above:

public class Response
    {
        public readonly int StatusID;                  // like 1111
        public readonly int UserID;                     // like 11111
        public readonly string MediaID;             // like abc123
        public readonly string MediaUrl;            // Something like this http://twitpic.com/abc123
        public readonly string MiniImage;         // Mini Thumbnail URL
        public readonly string ThumbImage;     // Thumbnail URL
        public readonly bool Status;                  // True = Success | False= Fail  
        public readonly int ErrorCode;                 // err_code= 1001 - Invalid twitter username or passwor
                                                        // err_code= 1002 - Image not found
                                                        // err_code= 1003 - Invalid image type
                                                        // err_code= 1004 - Image larger than 4MB 
        public readonly string ErrorMessage;     //Will contain the sorry excuse for not doing ur job  
                                                         //Invalid twitter username or password
        public Response(int statusid, int userid, string mediaid, string mediaurl) //to be called, when Method = UploadAndPost
        {
                    StatusID = statusid;
                    UserID = userid;
                    MediaID = mediaid;
                    MediaUrl = mediaurl;
                    MiniImage = "http://twitpic.com/show/mini/"+mediaid;
                    ThumbImage = "http://twitpic.com/show/thumb/"+mediaid;;
                    Status = true;
                    ErrorCode = 0;
                    ErrorMessage = "";
        }
        public Response(string mediaid, string mediaurl) //to be called, when Method = Upload
        {
            StatusID = 0;
            UserID = 0;
            MediaID = mediaid;
            MediaUrl = mediaurl;
            MiniImage = "http://twitpic.com/show/mini/" + mediaid;
            ThumbImage = "http://twitpic.com/show/thumb/" + mediaid; ;
            Status = true;
            ErrorCode = 0;
            ErrorMessage = "";
        }
        public Response(int errorcode, string message) //to be called, when error occurs
        {
                    StatusID = -1;
                    UserID = -1;
                    MediaID = "";
                    MediaUrl = "";
                    MiniImage = "";
                    ThumbImage = "";
                    Status = false;
                    ErrorCode = errorcode;
                    ErrorMessage = message;
        }
        public Response(string message)
        {
            Status = false;
            ErrorCode = 0; //there is some internal problem
            ErrorMessage = message;
        }
    }

You can run a quick demo of the Library, by creating an Instance in Object test bench and invoking the UploadAndPost method.

In case you want the source code, please download it from here

Ok! The thing is that TwitPic API is not that much complex, since all TwitPic provides is that it lets you post your funny/sad looking pictures or any picture you want to post on it, so it can be shared on twitter or any other site.

Its pretty much easy to implement all you have to know is how to create a web request, parse a XML, and post Multipart/form-data. You can get complete reference to TwitPic API here: http://twitpic.com/api.do

Since, hosting pictures is a part of some web applications that, I write and will write in future. So, I wrote my own library in .NET framework, that I can use to post pictures on TwitPic. As usual being a lazy guy and considering that code and methods involved are straight forward, I’m not providing the details here but, still I’m giving link to the CodePlex hosted project page, where you can download the library and complete source code (under MS-Pl License)

I have documented code at many places, wherever I thought was needed. So, there is very small possibility that you would say the “Holy F Word” while going through it, still if you may want to say so.

CodePlex Project Link http://twipli.codeplex.com

To know more about it, go to http://www.codeplex.com/XBC

Edit: Just released XBC V2.0

Features

• Presence Detection
• Presence Notification
• Buzzing
• Ask Yes/No Questions
• Send Message Pop UP
• Sits in SysTray, and show notifications
• AutoComplete for some common messages