My SDP 2011 Lecturer Interview

Last week SELA conducted a LIVE interview with all of the speakers at SDP 2011 (Sela Developer Practice conference).

You can catch my interview on the new Sela College Channel:

http://www.sela.co.il/y/ArikSprint11

or on YouTube:

In my interview I talked about the presentation I’ll deliver on March 15 in the Client track on the topic WPF + Silverlight + Windows Phone 7 = 3-Screens Development where I’ll show how to develop an application to WPF, Silverlight and Windows Phone 7, while maintaining a single code base. Also I plan to show some Azure features.

Hurry up and register - Fun is guaranteed!

That’s it for now,
Arik Poznanski.

Searching Twitter on Windows Phone 7

In the previous post we’ve seen how to get list of trends on twitter.
On this post we continue to explore twitter service. We will see you how to search for twits on twitter.

Searching Twitter

Twitter exposes a JSON-based search service in the following address:

http://search.twitter.com/search.json?q={0}

where {0} should be replaced with your search term.

The results are returned in JSON data format, so we will use again the DataContractJsonSerializer. For more details on how to use it, check out the previous post.

Defining Twit and TwitterResults

Similarly to what we’ve done in the previous post, we need to declare some C# model classes that will be used to parse the twitter JSON results.

Note that the twit text should be html-decoded before using it, so I’ve added a DecodedText property to do the job.

Implement the Twitter Search Service

We will implement a static method named TwitterService.Search that will receive the search term as its first parameter and a few delegates to allow our class to work asynchronously:

• Action<IEnumerable<Twit>> onSearchCompleted, which will be called when the twitter search is complete.
• Action<Exception> onError, which will be called if there is an error while searching twitter.
• Action onFinally, which will be called always, whether there was an exception or not. Think of it as the finally section on a common try-catch block.

So the method signature will be:

To search twitter we will use the WebClient class, yet again:

where TwitterSearchQuery is defined as follows:

The rest of the code handles the different delegates: on SearchCompleted, onError, onFinally. I bring here the method in its full:

Using the Twitter Search Service

Using the service is easy:

There is a sample application which can be downloaded here.

Note: this code was first published as part of the “Using Pivot and Panorama Controls” lab found in the Windows Phone Training Kit for Developers, which I wrote for Microsoft.

That’s it for now,
Arik Poznanski.

CodeProject

Get Twitter Trends on Windows Phone 7

In this post I will show you how you can get the list of trends on twitter.
On the next post I’ll show you how you can get the twits related to these trends and generally search twitter for twits.

What The Trend?

Twitter provides a cool site named http://whatthetrend.com/ where you can see the 10 topics which are most discussed currently on twitter.

This site also provides us a web service that returns its results in JSON data format.
The service can be accessed using the following URL:

http://api.whatthetrend.com/api/v2/trends.json?api_key={0}

where {0} should be replaced with your generated application key.

Generate Application Key

Since the twitter trends service provider limits its access using an application key, you must create one.

To do this, go to the site http://api.whatthetrend.com/ , on the right side you have a section titles "Request API key". By filling a small form you can immediately get a free application key which you can use.

Parsing JSON Data

The data returned from http://whatthetrend.com/ is in JSON data format. We would like to parse this data and convert it to C# classes.

To do so, we will use the class DataContractJsonSerializer which resides in the assembly System.ServiceModel.Web.dll.
The first thing we need to do is to add a reference to this assembly.

The service returns following JSON formatted data:

{"api_version":"2.0","as_of":"2011-02-05 14:39:19","trends":[{"name":"#scariestwordsever","trend_id":"201146","url":"http:\/\/search.twitter.com\/search?q=%23scariestwordsever","category_id":"9","category_name":"Meme","query":"#scariestwordsever","description":{"created_at":"2011-02-04T09:05:27+00:00","blurb_id":"322542","text":"Users are tweeting words\/phrases that would be the scariest to ever hear.","score":"1"},"first_trended_at":"2011-02-04T05:27:55+00:00","last_trended_at":"2011-02-05T14:35:01+00:00","newly_trending":"0","trend_index":"2","locked":false},{"name":"#thebadbehaviourtour","trend_id":"201678","url":"http:\/\/search.twitter.com\/search?q=%23thebadbehaviourtour","category_id":"14","category_name":"Other","query":"#thebadbehaviourtour","description":{"created_at":"2011-02-05T11:56:09+00:00","blurb_id":"322813","text":"@PlanetJedward aka John and Edward have announced new tour dates! @planetJedward are reply to as many fans as they can who put #TheBadBehaviourtour.","score":"0"},"first_trended_at":"2011-02-05T09:18:50+00:00","last_trended_at":"2011-02-05T14:35:01+00:00","newly_trending":"0","trend_index":"3","locked":false},
...
]}

Yea, this looks scary, but I’ve highlighted the interesting parts.
What we have here is a structure that have the properties:

• api_version
• as_of
• trends

The type of the trends property is an array of structures, each has the following properties:

• name
• trend_id
• url
• category_id
• category_name
• query
• description
• first_trended_at
• last_trended_at
• newly_trending
• trend_index
• locked

The description property is itself a structure that has the following properties:

• created_at
• blurb_id
• text
• score

All we need to do to get this information in an easy C# way is to define model classes which will have the same properties.

to parse the data into these objects we use the DataContractJsonSerializer:

where stream is a Stream object which contains the data in JSON format.

Implement the Get Trends Service

Now that we know how to parse the results, lets wrap this all in a method.

Our GetTrends method will receive a few delegates as parameters to allow our class to work asynchronously:

• Action<IEnumerable<Trend>> onGetTrendsCompleted, which will be called when the trends are ready to be processed.
• Action<Exception> onError, which will be called if there is an error while getting the trends.
• Action onFinally, which will be called always, whether there was an exception or not. Think of it as the finally section on a common try-catch block.

So the method signature will be:

To get the trends we will use the WebClient class:

Where WhatTheTrendSearchQuery is defined as follows:

The rest of the code handles the different delegates: onGetTrendsCompleted, onError, onFinally. I bring here the method in its full:

Using the Twitter Trends Service

As usual, the end result is very easy to use, simply call TwitterService.GetTrends static method and pass a delegate for the “completed” notification.

There is a sample application which can be downloaded here.

Note: this code was first published as part of the “Using Pivot and Panorama Controls” lab found in the Windows Phone Training Kit for Developers, which I wrote for Microsoft.

That’s it for now,
Arik Poznanski.

CodeProject

Search Digg on Windows Phone 7

Following is another utility class I wrote to help me search Digg results asynchronously on a Windows Phone 7 application.

I will present how it was written and then how to use it. At the end of this post you can find a sample application that contains all the code.

How to Search Digg?

Define DiggStory

First we define a model class that will hold a single Digg entry. This class will have the following properties:

• Title – title of the Digg entry
• Description – description of the Digg entry
• Link – link to the Digg entry
• Diggs – number of diggs in Digg

Add Assembly

In the following implementation I use Digg Search API which returns XML based results, so I‘m using LINQ to XML to easily parse the output.

In order to do so, we will add a reference to the assembly System.Xml.Linq.dll

Generate Application Key

Like most service providers, Digg also requires you to generate an application key for your application. This helps them know who uses their service and allow them to limit the requests from a single consumer.

I found the following application key to work, but I suggest you find a way to generate a new one in commercial apps.

Implement the Digg Search Service

Querying the Digg service is rather easy. Just use the following link:

http://services.digg.com/search/stories?query={0}&appkey={1}

Where {0} should be replaced with your search term and {1} should be replace with your application key.

So our Search method will receive the search term as a parameter.
In addition, since we want our class to work asynchronously we will accept as parameters a few more delegates:

• Action<IEnumerable<DiggStory>> onSearchCompleted, which will be called when the Digg results are ready to be processed.
• Action<string, Exception> onError, which will be called if there is an error while searching Digg. The first parameter for the delegate is the search term and the second is the exception.
• Action onFinally, which will be called always, whether there was an exception or not. Think of it as the finally section on a common try-catch block.

So the method signature will be:

To run the search we will use the WebClient class:

where DiggSearchQuery is defined as follows:

The result of the search is an XML string, so we use LINQ to XML to parse it:

The rest of the code handles the different delegates: onCompleted, onError, onFinally. I bring here the method in its full:

Using the Digg Search Service

Using the class is very easy, just pass the required search term and a delegate for the “completed” notification.

There is a sample application which can be downloaded here.

Note: this code was first published as part of the “Using Pivot and Panorama Controls” lab found in the Windows Phone Training Kit for Developers, which I wrote for Microsoft.

That’s it for now,
Arik Poznanski.

CodeProject

Reading RSS items on Windows Phone 7

Following is a utility class I wrote to help me read RSS items asynchronously on a Silverlight for Windows Phone 7 application.

I will present how it was written and then how to use it. At the end of this post you can find a sample application that contains all the code.

How to read RSS?

Add Helper Assembly

The first thing we need to do is to add a reference to the assembly, System.ServiceModel.Syndication.dll which contains classes that can parse RSS feeds.

This assembly is part of the Silverlight 3 SDK. It isn’t part of the Windows Phone 7 SDK, but there is no problem in using it there. You can find the file under:
%ProgramFiles%\Microsoft SDKs\Silverlight\v3.0\Libraries\Client\System.ServiceModel.Syndication.dll

You will get the following warning, just ignore it, it works.

Define RssItem

Before we get to business, let’s define a model class that will encapsulate the data of a single RSS item.

Our RssItem class will hold the following properties: Title, Summary, PublishedDate and Url. In addition I provide a PlainSummary property that will hold a plain text version of the RSS item. Usually the summary has HTML tags that we just want to ignore, thus PlainSummary for the rescue.

Implement The RSS service

The RSS service will get the RSS feed URL as a parameter.
In addition, since we want our class to work asynchronously we will accept as parameters a few more delegates:

• Action<IEnumerable<RssItem>> onGetRssItemsCompleted, which will be called when the RSS items are ready to be processed.
• Action<Exception> onError, which will be called if there is an error while getting the RSS items.
• Action onFinally, which will be called always, whether there was an exception or not. Think of it as the finally section a common try-catch block.

So the method signature will be:

To get the feed XML we will use the WebClient class:

The actual RSS parsing is done using the SyndicationFeed class from our helper assembly:

The rest of the code is for handling the different delegates: onCompleted, onError and onFinally. I bring here the method in its full:

Using the RSS Service

Using the class is very easy, just provide the URL as the first parameter and a delegate for getting the “completed” notification.

There is a sample application which can be downloaded here.

Note: this code was first published as part of the “Using Pivot and Panorama Controls” lab found in the Windows Phone Training Kit for Developers, which I wrote for Microsoft.

That’s it for now,
Arik Poznanski.

CodeProject