C#

Simple helper method to detect the last page of API data (C#)

When you are working with APIs from web services, you probably ran already into the same problem that I did recently: how to detect if we are on the last page of possible API results.

Some APIs (like WordPress) use tokens to be sent as parameter  with your request, and if the token is null or empty you know that you have reached the last page. However, not all APIs are working that way (for example UserVoice).

As I am rewriting Voices Admin to be a Universal app, I came up with a simple but effective helper method that allows me to easily detect if I am on the last page. Here is what I did:

	public static bool IsLastPage(int total, int countperpage, int current)
        {
            bool value = false;

            if (current < Convert.ToInt32(Math.Ceiling(Convert.ToDouble(total)/countperpage)))
            {
                value = false;
            }

            if (current == Convert.ToInt32(Math.Ceiling(Convert.ToDouble(total)/countperpage)))
                value = true;

            return value;
        }

As you can see, I need the number of total records that can be fetched (which is returned by the API) and the property for the number per page (which is one of the optional parameters of the API). On top, I need the current page number to calculate where I am (which is also an optional parameter of the API and returned by the API result).

Now I simply need to divide the total records by the result count per page to get how many pages are used. Using the Math.Ceiling() method, I always get the correct number of pages back. What does the Math.Ceiling() method do? It just jumps up to the next absolute number, also known as “rounding toward positive infinity”.

Example: if you have 51 total records and a per page count of 10, the division will return 5.1 (which means there is only one result on the 6th page). However, we need an absolute number. Rounding the result would return 5 pages, which is wrong in this case. The Math.Ceiling() method however returns the correct value of 6.

Setting the method up as a static Boolean makes it easy to change the CanExecute property of a button for example, which will be automatically disabled if we just have loaded the last page (page 6 in my case).

As always, I hope this is helpful for some of you.

Happy coding, everyone!

Posted by msicc in Dev Stories, win8dev, wpdev, 2 comments

Goodbye Telefónica (Germany), Hello ShareCommService (Switzerland)

Yes, you read that right. Today was my last work day at Telefónica, where I worked since June 2007. During that time, I learned a lot about how good customer service should be, and even more about mobile networks and mobile devices (phones, tablets and more). During that time, I also started my dev story in my spare time – all because there was not a single fishing knots application available for Windows Phone (read more here).

This lead to get recognized also within Telefónica as a developer, and so I was asked to concept and develop the application Friends & You (nope, you can’t download it as it is an internal app).  I learned a lot about how corporate apps aren’t that easy to concept and build during that time, as well as as how restrictive corporate rules can be. After all, I had a few challenges to complete. Thanks to Friends & You, I was also able to dive into the world of Xamarin, where I learned a lot about the application structures of Android and iOS (which will be helpful for eventually porting some of my Windows Phone apps to those two).

I want to say thanks to my colleagues, you´re awesome! Keep up the great work you´re doing in Customer Service.

Back in September then, I opened up my Twitter app and the first tweet I read was this one:

image

I opened the attached document and read the job description. As an self-thought developer, I first was about to close it and put it aside as “read and done”.

Due to the head count freeze at Telefónica after acquiring e-Plus from KPN, there are no chances to become a real full time developer within Telefónica for the next time. But that is what I want to do. After reopening the document and reading it again, I decided to get in contact with Roman Mueller (who I knew from Twitter already).

We talked about the job itself and the circumstances behind the announcement. After a few talks and a visit in Switzerland, the decision was made. I am starting the next chapter of my developer story in January, moving to Switzerland, where I will add deeper SQL knowledge, WPF and a lot more to my development knowledge.

At this point, I want to thank ShareCommService and especially Roman for all the help I received already to make this all happen and get started.

It is going to be an exciting journey for me (and my family), and we are ready to go.

Happy coding everyone!

Posted by msicc in Dev Stories, 1 comment

WordPressUniversal – a PCL library for WordPress based C# mobile apps

WP_CSharp_Lib

As I have already developed a news reader app for my blog, I got asked quite a few times if I want to share my code to help others creating their apps. As I need to redesign my blog reader to match the latest OS features of Windows and Windows Phone, I decided to create my WordPressUniversal library.

Automattic, the company behind WordPress, integrated a powerful JSON API into their JetPack plugin. My library is based on this API. Please make sure the JSON API is active on the blog you are developing your app for.

The library currently provides the following features:

  • getting a list posts or pages
  • getting a list of all categories
  • getting a list of comments for the site and single posts
  • supports Windows Phone 8 & 8.1 Silverlight, Windows Phone 8.1 RT, Windows 8, Xamarin.iOS and Xamarin.Android

The library deserializes all data into C# objects you can immediately work with.

It is still a work in progress, but as it provides already a bunch of options to get you started, I am making this public already.

I am constantly working on the library, so be sure to follow the project along.

Note: JetPack’s JSON API does not support guest commenting at the moment. I already reached out to Automattic to (hopefully) find a solution for this. If you cannot wait, Disqus has a portable solution for Windows Phone apps.

Please make sure to see the documentation on my GitHub page.

If you have any questions, idea, wishes for me, just post a comment here or ping on Twitter.

Happy coding everyone!

Posted by msicc in Dev Stories, win8dev, wpdev, Xamarin, 17 comments

Book review: iOS Development with Xamarin Cookbook (Dimitris Tavlikos)

I love to learn and expand my knowledge. Because of this, I was absolutely happy when I was asked for a book review about Dimitris’ iOS book.

The book is a huge collection of iOS recipes using Xamarin. The first three chapters are going deeply into the UI of an iOS application, looking on a lot (almost all) possible aspects of UI elements. What I like very much is that the author shows the code, usually with a step by step guide, and after that delivers a detailed explanation why something works in the way it does.

The next two chapters are all about creating and displaying data, files and sqlite, providing the same experience as the first chapters.

The sixth chapter is all about consuming services, such as web services, REST services or even WCF services (I wasn’t even aware of this being possible). Very good starting point for so many app ideas.

So far, the book shows already a lot of what we can do with Xamarin. But modern apps often contain media content: videos, photos, capturing media – this is what chapter 7 is all about.

Like all modern Smartphone operating systems, iOS provides some methods to let our apps interact with the OS. The 8th chapter is all about those interactions, like contacts, mail and more and has the matching real world scenarios.

The most usable apps use a device’s sensors, touch and gestures. Of course, with Apple being the leader in this space for a long time (we just need to be fair in this point), iOS has a lot of APIs for these. Chapter nine has some good recipes to help us with improving our app’s UX.

If your app needs location services and maps, chapter 10 is your friend. It shows you how to interact with Apple’s map services, add annotations and a lot more.

Users love when apps have some nice animations when something changes in an app. iOS provides a lot of options, and chapter 11 explains a lot about animations and drawing methods.

One of the most important parts when developing an app is lifecycle handling. As with any other OS, also iOS has its specific methods to handle the lifecycle. Background operations are part of this handling. In chapter 12, Dimitri tells us a lot about handling the states of an app as well as background operations.

Chapter 13 consists of tips and recipes for localization of an iOS app.

One of the most important steps when creating an iOS app is deploying the app. Apps should of course be tested on real devices, and this what chapter 14 is about – but not only. Also the required steps to prepare and app for submission as well as the submission to the store are explained.

The final chapter contains some additional recipes that can make your app more valuable like content sharing or text-to-speech.

Conclusion

I only began with Xamarin.iOS a few month ago. This book provides a great insight into development for iOS using the Xamarin IDE. As I said already, I like the approach of showing code first and then explaining what it does exactly and provide additional info if suitable. This book is absolutely worth every single cent if you want to start with iOS and Xamarin.

If you’re interested in the book, you’re just a click away: http://bit.ly/1tnxmGX

Note: This post was completely written on my phone. If you find typos, you can keep them ;-).

Posted by msicc in Dev Stories, Xamarin, 0 comments

Book review: Learning Windows Azure Mobile Services for Windows 8 and Windows Phone 8 (Geoff Webber-Cross)

During the last months, I used the few times of my spare time when I wasn’t in the mood for programming to read Geoff’s latest book for diving deeper into Azure Mobile Services. Geoff is well known in the community for his Azure experience, and I absolutely recommend to follow him! I am really glad he asked me to review his book and need to apologize that it took so long to get this review up.

The book itself is very well structured with a true working XAML based game that utilizes both Windows 8 and Windows Phone 8 and connects them to one single Mobile Service.

Even if you are completely new to Azure, you will quickly get things done as the whole book is full of step-by-step instructions. Let’s have a quick look on what you will learn while reading this book:

  1. Prepare your Azure account and set up your first Mobile Service
  2. Bring your Mobile Service to life and connect Visual Studio
  3. Securing user’s data
  4. Create your own API endpoints
  5. use Git via the console for remote development
  6. manage Push Notifications for both Windows and Windows Phone apps
  7. use the advantages of the Notification hub
  8. Best practices for app development – some very useful general guilty tips!

I already use a Mobile Service with my Windows Phone App TweeCoMinder. I have already started a Windows 8 version of that app, which basically only needs to be connected to my existing Azure Mobile Service to finish it.

Screenshot (359)

While reading Geoff’s book, I learned how I effectively can achieve this and also improve my code for handling the push notifications on both systems. The book is an absolutely worthy investment if you look into Azure and Mobile Services and has a lot of sample code that can be reused in your own application.

As this is my first book review ever, feel free to leave your feedback in the comments.

You can buy the book right here.

Happy coding, everyone!

Posted by msicc in Azure, Dev Stories, win8dev, wpdev, 0 comments

How to create a time based & cancelable BackgroundWorker for Windows Phone (and others)

backgroundworkerTimebased

While working on my current project, I needed a solution for a running code with a time offset. Well, you might say, no problem after all, and it is true.

The challenge at this point was to find a way to keep it cancelable at any time. And so the fun started.

After digging a bit deeper into the MSDN documentation, the BackgroundWorker class already have a bunch of methods and properties that are very helpful for this case.

As it is always the case when you work with multiple threads, it can cause some headache. But I got around it and thought it might be helpful for some of you.

Here is how I solved the scenario:

First, declare a static BackgroundWorker so you need to set it up only once on the page you want to use it. In the Loaded or OnNavigatedTo event, we are instantiating our BackgroundWorker.

worker = new BackgroundWorker();
worker.WorkerSupportsCancellation = true;
worker.WorkerReportsProgress = true;

Now, let’s add two very important properties: WorkerSupportsCancellation and WorkerReportsProgress. Both need to be set to true, otherwise you will get one InvalidOperationException after the other when running the code.

In my case, I created a separate method to start the BackgroundWorker and hook up to all important events:

        private void RunBackgroundWorker()
        {
            worker.RunWorkerCompleted += worker_RunBackgroundWorkerCompleted;

            //delegating the DoWork event
            worker.DoWork += ((s, args) =>
            {
                //generating a loop
                for (int i = 0; i < 100; i++)
                {

                    if (worker.CancellationPending == true)
                    {
                        //set cancel to true to finish the cancellation on the next run in the loop
                        args.Cancel = true;
                    }
                    else
                    {
                        //calculate your time: seconds * 1000 / 100
                        Thread.Sleep(50);
                        worker.ReportProgress(i);
                    }
                }
            });

            //can be used to fill a progress bar/show percentage
            worker.ProgressChanged += worker_ProgressChanged;

            //start the BackgroundWorker
            worker.RunWorkerAsync();
        }

You might notice that I created a loop that runs up to 100. This is necessary for my solution, as this is the key to make the BackgroundWorker cancelable in my solution. Every 50 milliseconds, the CancellationPending property gets checked as I am looping through until the count reaches 100.  I am setting an offset of 50 milliseconds, as I want to have a total offset of 5 seconds.

Next, let us set up a button that cancels the background task (can be used in other events/methods, too):

public void CancelButton_Click(object sender, RoutedEventArgs e)
{
    //check this always to avoid InvalidOperationExceptions
   if (worker.WorkerSupportsCancellation == true)
   {
         //request cancellation of the BackgroundWorker
         //this sets the CancellationPending property to true
        worker.CancelAsync();
    }
 }

Important: Always check if the Cancellation is supported by your BackgroundWorker to avoid those ugly InvalidOperationExceptions. Then, simply call the CancelAsync() method of your BackgroundWorker to set the CancellationPending property to true.

When the BackgroundWorker has completed (or cancelled), the value of the CancellationPending property is passed to the RunBackgroundWorkerCompletedEvent, where you can simply use the e.Cancelled property to continue your code (which will then be back on your main application thread):

private void worker_RunBackgroundWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    if (e.Cancelled == true)
    {
       //your code in case the BackgroundWorker was cancelled
    }
    else
    {
       //your code in case the BackgroundWorker was running until the end
    }
}

The last event I want to mention is the ProgressChanged event. It can be used to display a percentage or similar things, I just use it to see when the cancellation gets active:

private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
     //your code here, for example display percentage or fill a progress bar

     //use the line below to check the percentage and if CancellationPending property gets changed
     //Debug.WriteLine(e.ProgressPercentage + "  " + worker.CancellationPending);
}

With this few methods we can create a time based  offset on a BackgroundWorker while keeping it cancelable at any time. The code above  should work in similar form also on other platforms like Windows 8 or Xamarin.

As always, I hope this will be helpful for some of you.

Happy coding!

Posted by msicc in Dev Stories, wpdev, 1 comment

Getting productive with WAMS: respect time zone offset for every single user

time_Azure

In my second post about WAMS I will show you how to respect the time zone of every user.

If you have users that are from all over the world, they have all different time zones. Your Mobile Service script runs always at UTC time, and every user gets the same date & time if you send them push notifications or update a live tile for example. Users don’t want to calculate the time zone differences, so we need to handle that for them.

UTC time is the time since 01/01/1970 00:00 in milliseconds. If we know this, it is somewhat easy to show users their local date and time.

Let’s have a look at the Windows Phone code.

To get the local time zone in our Windows Phone app, we only need three lines of code:

TimeZoneInfo localZone = TimeZoneInfo.Local;
DateTime localTime = DateTime.Now;
TimeSpan offsetToUTC = localZone.GetUtcOffset(localTime);

As you can see, we are getting the local time zone first. This is essential as this one is UTC based. Then we are creating a TimeSpan on our actual DateTime object to get the offset. To make this TimeSpan working on our Azure Mobile Service, which uses JavaScript, we need to convert it to milliseconds. That is the value that has an equal value on all programming languages.

useritemLookUp.TimezoneOffset = offsetToUTC.TotalMilliseconds;

This is the final line of code, which is used to update our user’s item in our SQL table row (for example).

Let’s have a look at the Azure code.

The code is similar to our Windows Phone part. First, we need to fetch the time zone offset from our SQL table:

var sql = "select * from users";

mssql.query(sql, {
        success: function (results) {
            if (results.length > 0) {
                for (var i = 0; i < results.length; i++) {
                    userResult = {
                                        TimeZoneOffset: results[i].TimezoneOffset,
                                        }

TimeZoneOffset = userResult.TimeZoneOffset;

This way, we can run through our whole table on an Azure Script and calculate the correct time, which is pretty easy to achieve:

var d = new Date();
var locald = new Date(d.getTime() + TimeZoneOffset);

These two lines generate the local time in Milliseconds for the specific user entry. You don’t have to worry whether a user is before or after UTC, it will always calculate the correct time.

If you want to use it for example to show the updated time to your users, you can format the time like I described earlier in this post.

That’s all about respecting local time for your users with Windows Azure and Windows Phone.

Happy coding everyone!

Posted by msicc in Azure, Dev Stories, 0 comments