Saturday, October 4, 2014

Returning multiple values from a method

During your programming escapades you are sure to come across an instance when you need to return multiple values from a method.

The traditional ways of doing it are:

(i) to create an object of a class, instantiate it and assign values to the object inside the method and then return the object from the method, or

(ii) to assign values to multiple global variables inside the method and then access them elsewhere, or

(iii) to use an out parameter to return the updated value back to the calling method, or

(iv) to use a ref parameter to modify the referenced parameter directly from inside the called method.


Well, there is another lesser-known way in .Net that allows you to return multiple values from a method without having to create an object or multiple variables, it is a feature called Tuple.

Here is some sample code in C# that shows you how to create and use a Tuple to return multiple values from a method:

public Tuple<int, string, string> GetEmployee()
{
    int employeeId = 23;
    string firstName = "John";
    string lastName = "Doe";

    //Create a tuple and return
    return Tuple.Create(employeeId, firstName, lastName);
}

Regards,
Paras Wadehra
Microsoft MVP
Twitter: @ParasWadehra

Thursday, August 21, 2014

How to send email from your Windows Phone 8.1 app

As part of the API changes made in the new Windows Phone 8.1 XAML programming model, the EmailComposeTask - and several other tasks - that were available in the Microsoft.Phone.Tasks namespace in Windows Phone 8 are no longer available.

Most of these have been replaced with a new way of performing the same tasks. For sending an email from within your app, the old way in Windows Phone 8 was as follows:

OLD WAY
========

EmailComposeTask emailComposeTask = new EmailComposeTask();
emailComposeTask.Subject = "Subject";
emailComposeTask.To = "support@developer.com";
emailComposeTask.Show();


The new way in Windows Phone 8.1 to send an email from your app is as follows:

NEW WAY
=========

// Define Recipient
EmailRecipient sendTo = new EmailRecipient()
{
    Name = "Name of Recepient",
    Address = "support@developer.com"
};

// Create email object
EmailMessage mail = new EmailMessage();
mail.Subject = "this is the Subject";
mail.Body = "this is the Body";

// Add recipients to the mail object
mail.To.Add(sendTo);
//mail.Bcc.Add(sendTo);
//mail.CC.Add(sendTo);

// Open the share contract with Mail only:
await EmailManager.ShowComposeNewEmailAsync(mail);


Have fun,
Paras Wadehra
Microsoft MVP - Windows Platform Development
http://twitter.com/ParasWadehra
https://www.facebook.com/WindowsPhoneDeveloper
My WP Apps

Saturday, August 2, 2014

Xamarin Forms Shared project template error

The new Xamarin Forms Shared Project Template has a bug which causes the Windows Phone build to fail out of the box. You might see an error like:

The 'ProductID' attribute is invalid - The value 'b79569cb-1898-4dab-9173-afe40fa8559c' is invalid according to its datatype 'http://WPCommontypes:ST_Guid' - The Pattern constraint failed.

Note that the error message you receive might be a little different depending on what value is not defined properly. You are in luck though, as there is a simple fix for this.

You can fix the issue by modifying the WMAppManifest.xml file in your Windows Phone project. You need to add curly braces (are there any other style?) around the GUID values for the ProductID and PublisherID attributes. In some cases there might be other GUID values that are missing the curly braces too so add them there as well.

And that's it! This should resolve your error and get you on your path to a successfully building application :)

Cheers,
Paras Wadehra
Microsoft MVP - Windows Platform Development
http://twitter.com/ParasWadehra
https://www.facebook.com/WindowsPhoneDeveloper
My WP Apps

Wednesday, June 25, 2014

How to make your Windows Phone app vibrate?

There are 2 simple ways to make your Windows Phone app vibrate the device.

The first method makes use of the VibrateController class in the Microsoft.Devices namespace:

            VibrateController vibrateController = VibrateController.Default;
            vibrateController.Start(TimeSpan.FromSeconds(2));
            vibrateController.Stop();

The second method makes use of the VibrationDevice class in the Windows.Phone.Devices.Notification namespace:

            VibrationDevice vibrationDevice = VibrationDevice.GetDefault();
            vibrationDevice.Vibrate(TimeSpan.FromSeconds(3));
            vibrationDevice.Cancel();

In both these instances, the vibration will automatically stop after the amount passed as TimeSpan has elapsed.

You can call the corresponding Stop or Cancel method of the class to stop the vibration before the TimeSpan passed has elapsed.

Regards,
Paras Wadehra
Microsoft MVP
Twitter: @ParasWadehra

Wednesday, May 14, 2014

System.UnauthorizedAccessException: Access is denied

So you are coding up your next big app and cruising along, but suddenly you face an error like the following:

{System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()

Fear not, my friend, this is a simple case of Missing Capabilities.

For example, if you are trying to fetch the geolocation of a user, that means you are missing the ID_CAP_LOCATION capability. If you are coding a Windows Phone app, you need to open WMAppManifest.xml file in the designer in Visual Studio and then go to the Capabilities tab and select the checkbox next to ID_CAP_LOCATION.

Similarly, if you try to access other features and the corresponding capabilities are are not enabled you might see this error message as well.

Remember, there are 3 things that matter when accessing any device based features in your Windows apps: Capabilities, Capabilities, Capabilities.

Till next time,
Paras Wadehra
Microsoft MVP and Ambassador
Twitter: @ParasWadehra
FB.com/WindowsPhoneDeveloper
My WP Apps

Wednesday, March 26, 2014

1 Million Downloads, Part-2, App Statistics

This is Part-2 in a series of blog posts I am writing to detail my experiences to get to 1 Million downloads on Windows Phone.

In this post, for the first time ever, I will make public detailed info around my app statistics which will show you how my top apps have performed since launch. I will also correlate some spikes I've seen with promotions I've run or new updates I've launched. Please note that the charts you see below are not from the same time period or include up to date downloads count info.

I'll start with statistics for my most popular app, Dictionary:

Dictionary






























As you can see, getting featured in the Windows Phone Store really helps drive downloads for your app. The sustained organic growth period you see above is actually due to Dictionary winning first place in the Best Educational App category of the first-ever Windows Phone App Awards, beating competition from Microsoft and other competitors.

Now, let's take a look at SketchPad:


Again, the effect of getting featured in the Windows Phone Store clearly shows its benefits. I've been fortunate enough to have SketchPad featured in different countries across the world several times now.

Let's take a look at Unit Converter:


This chart shows you the bumps received in the download count just by updating the app to include new features and functionality. Users really like seeing their feedback being incorporated in the app.

Here's Events For Me:


This chart not only shows you the benefit of getting featured in the Windows Phone Store, but also getting a good review on WP Central. In this case, the WP Central review drove the most downloads in 1 day to the Events For Me app.

I've saved the best for the last though, be prepared to be flabbergasted, as I show you The DVLUP Effect. Here's a look at the downloads for my Chess game



And here's the interesting part. See that red circle with a minor bump on the road? That is what you see in the chart below.



This shows you how using campaigns from DVLUP, I was able to achieve The DVLUP Effect which dwarfed downloads from any other promotions. Soon after launch, in early 2012, the Chess game also won 1st place in Microsoft's You've Got Game competition.

Windows Phone Store placements and DVLUP Campaigns have been a god given gift for an indie developer like myself.

In Part 1 of this blog series, I shared the news about my apps hitting 1 Million downloads on Windows Phone and introduced you to my apps.
In Part 3 of this blog series, I will talk about mistakes made and lessons learned.
In Part 4 of this blog series, I will talk about monetization and promotion mechanisms I've used over the years and which ones have worked better than the others.

Cheers, 
Paras Wadehra
Do you DVLUP?
Twitter: @ParasWadehra

Thursday, March 20, 2014

1 Million Downloads

I am happy to report that my apps have surpassed the 1 Million download mark on Windows Phone.



This is the first post in a series of blog posts I will be writing about my lessons learned, mistakes made, best practices, monetization and promotion practices, among other things, so keep an eye out!

I've been able to get to this special landmark a few days before 3 year anniversary of my first app launching on Windows Phone.

I would love to share my development experience with you all, in hopes of helping all aspiring app developers out there.

My first app (or rather a game), Tic Tac Toe, launched in the store on 25-Mar-2011. I wrote this as a personal learning experience on Windows Phone. I included ads in the game and I soon started seeing some ad revenue trickling in. I used to get excited when I made 5c/day in ad revenue in early days - simply because it meant someone out there downloaded my game and was playing it. Soon I saw that number climbing up, 10c/day, 25c/day and soon I was seeing $1/day in ad revenue coming in.

By then I had already launched a couple more apps in the Windows Phone store, Transit Maps USA and Dictionary, the first Dictionary app on Windows Phone. It got featured in the Windows Phone Store and I immediately saw the effect of that as to the increase in my downloads and ad revenue. And since then I haven't looked back and launched new apps constantly on the platform, though in the last year I have been focused on updating my existing apps with new features rather than creating new apps, given the time constraints as this is a hobby outside of my job. I've been able to help create Windows Phone apps for some big name apps on the store as well along the way.

Given that I was developing apps at a rapid pace for the platform, I got accepted to receive early access to the Windows Phone Mango (WP 7.5) update in 2011, before it launched and subsequently to Windows Phone Apollo (WP 8) in 2012, as well.

My current apps on the Windows Phone platform include, in chronological release order:

As you will see from the list above, I launched a majority of my apps in 2011 and then focused on maintaining and updating those apps for the most part with a few other apps launching in 2012 and 2013. I have several unfinished projects that I need to find time to finish and polish to publish them in the store. I also have a wish list of many more apps that I want to develop.

When Windows 8 was announced, I ported my Unit Converter and Tic Tac Toe apps to that platform as well and saw some good download numbers for both of these apps.

In Part 2 of this blog series, I provide detailed breakdown of my app statistics and the download performance associated with major releases, updates and promotions.
In Part 3 of this blog series, I will talk about mistakes made and lessons learned.
In Part 4 of this blog series, I will talk about monetization and promotion mechanisms I've used over the years and which ones have worked better than the others.

Cheers,
Paras Wadehra
Do you DVLUP?
Twitter: @ParasWadehra