Porting your WebApi 2.2 app to Azure Service Fabric

Now, to start talking about this, you gotta know why this is spawned off instead of spawning off a “hello world” to service fabric. I’m back to writing after a long time and it’s only fitting I do share what I have been doing meanwhile.

Usually in a production scenario you’d end up with a case where you have your applications lying around in several tiers. To be honest, I’m pointing reference to a production environment which is microservices driven. If you’re reading this and questioning why I did that you probably want to go down here to get yourself started with the basic concepts of Azure Service Fabric.

Now, I hope you have familiarized yourself with service fabric by now and I can start talking about how you can port your existing IIS hosted Asp.net Web Api 2.2 application to a self-hosted statless web api service in Azure Service Fabric.

To get yourself started please install Azure Service Fabric local development environment in your machine from here and go through the set of instructions to get yourself started. When you’re done with these, you’d see Visual Studio come up with a new set of project types for service fabric.

And it would pretty much like the following:

servicefabricprojecttype

Now, before we click the that elusive OK button, we need to understand what are the tasks at hand here. We have to do two things here.

1. Make sure our web api 2.2 app is compatible with self host as it was using IIS.

2. Make sure we can salvage the same Visual Studio project we used for our web project.

Making sure the existing web api 2.2 app is compatible of self hosting:

  1. For number one, one might think it should be farely easy to port a IIS driven web api app to a self hosted app, the reality might not be that easy. First, make sure you have a OWIN startup class initiated. Usually you would have one if you are using OWIN. And you’d also need a Program.cs file which is standard one for a console application as now your web app would be  a self-hosted application. So go ahead and add these two files to your web project and if you need reference, both of them are shown here.
  2. Now, although you have a startup.cs and Program.cs initiated already, you still haven’t converted your web app project to a console application. To do so, please go over your project properties and  on the Applications section, select Output Type as Console Application and set the Program class as the Startup object. Now, if you forget to add Program.cs as startup object which you’d only be able to do after you have created that file with a static void Main(string[] args) initiated on it, as long as it is named Program.cs the project would invoke it automatically.
  3. If you are using anything from Microsoft.Owin.Host.SystemWeb library, please make sure that these wont work anymore for you. For example if you are using code segments like the following to resolve file path to your traditional web app deployment and subsidiary folders like App_data, it wont work anymore for you.
     string path = System.Web.Hosting.HostingEnvironment.MapPath(@"~/App_Data/EmailTemplates/");
    

    So for things like these you might have to resort yourself to solutions that resolves deployment path in a console application.

  4. Now, there are some other pranks too. If you are familiar with Asp.net Identity and use it for your default identity provider, you’re in for a treat. Usually when you develop a expirable token generation paradigm for email and passwords, you’d need to use a IDataProtectionProvider which is usually the MachineKeyDataProtectionProvider under the namespace of Microsoft.Owin.Host.SystemWeb.DataProtection which you’d probably ditch because you would be using owin self host/Katana now. So, expect a null there where you try something like app.GetDataProtectionProvider() where app is your IAppBuilder. I ran into this myself and thanks to Katana being open source, you just pick up the MachineKeyDataProtectionProovider class from here.Just make sure you use it as  IDataProtectionProvider like the following:
    using System;
    using System.Web.Security;
    using Microsoft.Owin.Security.DataProtection;
    
    namespace TaskCat.Lib.DataProtection
    {
        using DataProtectionProviderDelegate = Func<string[], Tuple<Func<byte[], byte[]>, Func<byte[], byte[]>>>;
        using DataProtectionTuple = Tuple<Func<byte[], byte[]>, Func<byte[], byte[]>>;
    
        ///
    <summary>
        /// Used to provide the data protection services that are derived from the MachineKey API. It is the best choice of
        /// data protection when you application is hosted by ASP.NET and all servers in the farm are running with the same Machine Key values.
        /// </summary>
    
        internal class MachineKeyDataProtectionProvider: IDataProtectionProvider
        {
            ///
    <summary>
            /// Returns a new instance of IDataProtection for the provider.
            /// </summary>
    
            /// <param name="purposes">Additional entropy used to ensure protected data may only be unprotected for the correct purposes.</param>
            /// <returns>An instance of a data protection service</returns>
            public virtual MachineKeyDataProtector Create(params string[] purposes)
            {
                return new MachineKeyDataProtector(purposes);
            }
    
            public virtual DataProtectionProviderDelegate ToOwinFunction()
            {
                return purposes =>
                {
                    MachineKeyDataProtector dataProtecter = Create(purposes);
                    return new DataProtectionTuple(dataProtecter.Protect, dataProtecter.Unprotect);
                };
            }
    
            IDataProtector IDataProtectionProvider.Create(params string[] purposes)
            {
                return this.Create(purposes);
            }
        }
    }
    

    And you’d need to do the same with MachineKeyDataProtector class and use it as a IDataProtector like the following:

    using System.Web.Security;
    using Microsoft.Owin.Security.DataProtection;
    
    namespace TaskCat.Lib.DataProtection
    {
        internal class MachineKeyDataProtector: IDataProtector
        {
            private readonly string[] _purposes;
    
            public MachineKeyDataProtector(params string[] purposes)
            {
                _purposes = purposes;
            }
    
            public virtual byte[] Protect(byte[] userData)
            {
                return MachineKey.Protect(userData, _purposes);
            }
    
            public virtual byte[] Unprotect(byte[] protectedData)
            {
                return MachineKey.Unprotect(protectedData, _purposes);
            }
        }
    }
    
    

    Then you can use it as your replacement of your old one from Microsoft.Owin.Host.SystemWeb.DataProtection. This is not really needed if you don’t use Asp.net Identity but of to good use if you land in the same problem.Now, hopefully your current web api app would be self hosted just fine if you try something like the following:

    // Start OWIN host
    using (WebApp.Start<Startup>(url: baseAddress))
    {
      Console.WriteLine("Press ENTER to stop the server and close app...");
      Console.ReadLine();
    }
    

Now, lets try salvaging that Visual Studio project as much as we can.

Project changes when it comes to Visual Studio

  1. Now, you can use the converted project but from my personal experience it would be easier for you if you just click the new ServiceFabric project button now and create a new Stateless WebApi project. You can port/reuse most of your code and as the boilerplates are already written, you don’t really have to rewrite that.
  2. If you want to keep the old project intact, you can of course reference the old project in the new stateless web api service project and use your old startup class to hook up the OwinCommunicationListener instead of the one that it comes with. But beware, nuget might make it a nightmare for you if dependencies are not met/mismatched.

Hope you guys have fun with Azure Service Fabric and if you really want to look for more how you can do you own stateless web api from scratch take a look here. If I find time, I’d write one too.

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Windows Phone For Newbies – Geofencing in Windows Phone 8.1 WinRT

Geofencing was one of the newest features Windows Phone 8.1 provided and for the developers it indeed was cool. Previously people did it their way but it’s always better to have an api in our hand. So, before digging into that i strongly suggest you guys to read my previous 2 articles if you haven’t done it already.

1. The Complete Reference of Map Control in Windows Phone 8.1 RT

2. Tracking Location in Windows Phone 8.1

These two would get you started pretty fast and you’d probably want that. If you already read my aforementioned 2 articles, I expect you know how to use a map control in Windows Phone 8.1. We’re going to need that later.

Geofencing:

Geofencing is a mechanism where you put a virtual boundary around a specific point of interest and you want to interact with the user when you arrive or leave that specific boundary. You seriously can do pretty amazing stuff with it actually.

Initial Work:

Now, let’s take a more practical approach to this, every time I go into my room, Im supposed to check my mails. But I usually forget that. How cool it would be if my phone reminds me every time I get into my room and tells me to check my mail?  😉

So, let’s go ahead and create a new Windows Phone app and name it GeoFencingTest. Now, lets see how to do that actually.

So, first of all go over your Package.appxmanifest file and go to the Capabilities Tab and select the Location capability.

Geofencing 1

Now, when you are done with that, let’s move on and start cracking. Before going deep lets get a basic UI running. And it looks like following:

GeoFencing - 2

And on the XAML part it looks like the following:

    &lt;Grid&gt;
        &lt;Grid.RowDefinitions&gt;
            &lt;RowDefinition Height=&quot;Auto&quot;&gt;&lt;/RowDefinition&gt;
            &lt;RowDefinition Height=&quot;4*&quot;&gt;&lt;/RowDefinition&gt;
            &lt;RowDefinition Height=&quot;8*&quot;&gt;&lt;/RowDefinition&gt;
        &lt;/Grid.RowDefinitions&gt;
        

        &lt;Grid Grid.Row=&quot;0&quot;&gt;
            &lt;TextBlock Text=&quot;GeoFencing Sample&quot; FontSize=&quot;25&quot; Margin=&quot;10&quot;/&gt;
        &lt;/Grid&gt;

        &lt;Grid Grid.Row=&quot;1&quot;&gt;
            &lt;Grid.ColumnDefinitions&gt;
                &lt;ColumnDefinition&gt;&lt;/ColumnDefinition&gt;
                &lt;ColumnDefinition&gt;&lt;/ColumnDefinition&gt;
            &lt;/Grid.ColumnDefinitions&gt;

            &lt;StackPanel Margin=&quot;10&quot;&gt;
                &lt;TextBlock Text=&quot;Longitude&quot; Margin=&quot;0,0,0,15&quot;  FontSize=&quot;20&quot;&gt;&lt;/TextBlock&gt;
                &lt;TextBlock Text=&quot;Latitude&quot;  Margin=&quot;0,0,0,15&quot; FontSize=&quot;20&quot;&gt;&lt;/TextBlock&gt;
                &lt;TextBlock Text=&quot;Altitude&quot;  Margin=&quot;0,0,0,15&quot; FontSize=&quot;20&quot;&gt;&lt;/TextBlock&gt;
            &lt;/StackPanel&gt;

            &lt;StackPanel Grid.Column=&quot;1&quot; Margin=&quot;10&quot;&gt;
                &lt;TextBlock Name=&quot;Longitude&quot; Margin=&quot;0,0,0,15&quot;  FontSize=&quot;20&quot;&gt;&lt;/TextBlock&gt;
                &lt;TextBlock Name=&quot;Latitude&quot;  Margin=&quot;0,0,0,15&quot; FontSize=&quot;20&quot;&gt;&lt;/TextBlock&gt;
                &lt;TextBlock Name=&quot;Altitude&quot;  Margin=&quot;0,0,0,15&quot; FontSize=&quot;20&quot;&gt;&lt;/TextBlock&gt;
            &lt;/StackPanel&gt;

        &lt;/Grid&gt;

        &lt;Grid Grid.Row=&quot;2&quot; Margin=&quot;10&quot;&gt;
            &lt;Grid.ColumnDefinitions&gt;
                &lt;ColumnDefinition Width=&quot;4*&quot;&gt;&lt;/ColumnDefinition&gt;
                &lt;ColumnDefinition Width=&quot;7*&quot;&gt;&lt;/ColumnDefinition&gt;
            &lt;/Grid.ColumnDefinitions&gt;
            &lt;Grid.RowDefinitions&gt;
                &lt;RowDefinition&gt;&lt;/RowDefinition&gt;
                &lt;RowDefinition&gt;&lt;/RowDefinition&gt;
                &lt;RowDefinition&gt;&lt;/RowDefinition&gt;
            &lt;/Grid.RowDefinitions&gt;

            &lt;CheckBox Content=&quot;Single Use&quot;&gt;&lt;/CheckBox&gt;
            &lt;TextBlock Grid.Row=&quot;1&quot; FontSize=&quot;20&quot; Text=&quot;Dwell Time&quot; Margin=&quot;0,8,0,0&quot;/&gt;
            &lt;TextBox Grid.Column=&quot;1&quot; Name=&quot;DwellTime&quot;  Grid.Row=&quot;1&quot;/&gt;

            &lt;Button x:Name=&quot;CreateGeoFencingButton&quot; Grid.Row=&quot;2&quot; Grid.ColumnSpan=&quot;2&quot; Content=&quot;Create GeoFence&quot; HorizontalAlignment=&quot;Stretch&quot; VerticalAlignment=&quot;Bottom&quot;/&gt;
            
        &lt;/Grid&gt;

    &lt;/Grid&gt;

Before going in deep on what is for what let’s get some basic stuff done. Let’s get our current location first.

Since you guys have seen in the last articles, it’s fairly easy to do so. All I’m doing here is get the current location using Geolocator and put the Latitude, Longitude and Altitude into the textblocks defined in the MainPage.xaml.

    public sealed partial class MainPage : Page
    {
        Geolocator geolocator = new Geolocator();
        CancellationTokenSource CancellationTokenSrc = new CancellationTokenSource();

        public MainPage()
        {
            this.InitializeComponent();

            this.NavigationCacheMode = NavigationCacheMode.Required;
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {

            InitializeLocation();

        }

        async private void InitializeLocation()
        {
            try
            {

                geolocator = new Geolocator();

                CancellationTokenSrc = new CancellationTokenSource();
                CancellationToken token = CancellationTokenSrc.Token;

                var position = await geolocator.GetGeopositionAsync(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(30)).AsTask(token);

                Longitude.Text = position.Coordinate.Point.Position.Longitude.ToString();
                Latitude.Text = position.Coordinate.Point.Position.Latitude.ToString();
                Altitude.Text = position.Coordinate.Point.Position.Altitude.ToString();
            }

            catch (Exception)
            {
                if (geolocator.LocationStatus == PositionStatus.Disabled)
                {
                    ShowMessage(&quot;Location Services are turned off&quot;);
                }

            }
            finally
            {
                CancellationTokenSrc = null;
            }

        }

        private async void ShowMessage(string message)
        {
            MessageDialog dialog = new MessageDialog(message);
            await dialog.ShowAsync();
        }
    }

The only thing that is interesting here is having a CancellationToken generated from a CancellationTokenSource. Usually these are used if you really want control over your task after it’s being fired, the rest of the procedure should look familiar as it’s a basic Geolocator usage to find current geolocation.

Setting up a GeoFence:

Now comes the setting up the actual GeoFence part and even this is fairly simple. The method looks like the following:

        Geofence geofence = null;
        int DefaultDwellTimeInSeconds = 0;
        private void SetupGeofence()
        {
            //Set up a unique key for the geofence
            string GeofenceKey = &quot;My Home Geofence&quot;;
            BasicGeoposition GeoFenceRootPosition = GetMyHomeLocation();

            double Georadius = 500;

            // the geocircle is the circular region that defines the geofence
            Geocircle geocircle = new Geocircle(GeoFenceRootPosition, Georadius);

            bool singleUse = (bool)SingleUse.IsChecked;

            //Selecting a subset of the events we need to interact with the geofence
            MonitoredGeofenceStates GeoFenceStates = 0;

            GeoFenceStates |= MonitoredGeofenceStates.Entered;
            GeoFenceStates |= MonitoredGeofenceStates.Exited;

            // setting up how long you need to be in geofence for enter event to fire
            TimeSpan dwellTime;

            dwellTime = DwellTime.Text!=&quot;&quot;? ParseTimeSpan(DwellTime.Text) : TimeSpan.FromSeconds(DefaultDwellTimeInSeconds);

            // setting up how long the geofence should be active
            TimeSpan GeoFenceDuration;
            GeoFenceDuration = TimeSpan.FromDays(10);

            // setting up the start time of the geofence
            DateTimeOffset GeoFenceStartTime = DateTimeOffset.Now;

            geofence = new Geofence(GeofenceKey, geocircle, GeoFenceStates, singleUse, dwellTime, GeoFenceStartTime, GeoFenceDuration);

            //Add the geofence to the GeofenceMonitor
            GeofenceMonitor.Current.Geofences.Add(geofence);

        }

        private TimeSpan ParseTimeSpan(string DwellTimeInSeconds)
        {
            return TimeSpan.FromSeconds(Double.Parse(DwellTimeInSeconds));

        }

        private static BasicGeoposition GetMyHomeLocation()
        {
            BasicGeoposition GeoFenceRootPosition;
            GeoFenceRootPosition.Latitude = 23.742766;
            GeoFenceRootPosition.Longitude = 90.417566;
            GeoFenceRootPosition.Altitude = 0.0;
            return GeoFenceRootPosition;
        }

Now, there’s quiet a lot to catch up.

The first one is definitely the GeofenceKey. Put a GeofenceKey in position just to identify a specific Geofence. I put s generic string to identify my home geofence.

Then I called up GetMyHomeLocation() method to set the geofence center to the location of my room. This will identify the center of our desired Geofence.

And the next thing to define is a radius that will define the radius of our circular geofence. We are using Geocircle object to define our geofence here, thus we are using a center and a radius in meters to defined our geofence. You can definitely see the next thing we did is define our geocircle. Actually the Geofence takes a Geoshape object to define it’s radius and currently only Geocircle is supported.

            string GeofenceKey = &quot;My Home Geofence&quot;;
            BasicGeoposition GeoFenceRootPosition = GetMyHomeLocation();

            double Georadius = 500;

            // the geocircle is the circular region that defines the geofence
            Geocircle geocircle = new Geocircle(GeoFenceRootPosition, Georadius);

Now, we have put a checkbox in our XAML named SingleUse. This is supposed to define whether our geofence would be used for only one time or not. You can set up temporary one time used geofence using this.


bool singleUse = (bool)SingleUse.IsChecked;

Now, the next thing we did is we defined how our desired geofence would be treated. Which events are we considering with this geofence? Should this be fired only when we get into that geofence or should this will only be considered when we exit the geofence, or even we remove the geofence? We can actually select all or a subset of that group. So we used Logical OR operator to add up all the cases we want our geofence to react upon.


            MonitoredGeofenceStates GeoFenceStates = 0;

            GeoFenceStates |= MonitoredGeofenceStates.Entered;
            GeoFenceStates |= MonitoredGeofenceStates.Exited;

Let’s move on into the time domain now. Now we need to figure how long we need to stay in our favourite geofence to trigger up it’s desired events. I put a textbox in front to define that in seconds, if that is defined, we fire out events from our geofence in that number of seconds and if not we fire out events in our default dwell time defined by 0 seconds.

            // setting up how long you need to be in geofence for enter event to fire
            TimeSpan dwellTime;

            dwellTime = DwellTime.Text!=&quot;&quot;? ParseTimeSpan(DwellTime.Text) : TimeSpan.FromSeconds(DefaultDwellTimeInSeconds);

You can even define how long a geofence should be up and running. Like I want my rooms geofence to be running for next 10 days.


            // setting up how long the geofence should be active
            TimeSpan GeoFenceDuration;
            GeoFenceDuration = TimeSpan.FromDays(10);

Even with that thing defined, one question remains, even though it will run for 10 days, when does the geofence gets activated so it can start counting to that defined 10 days. Answer is right below:


// setting up the start time of the geofence
            DateTimeOffset GeoFenceStartTime = DateTimeOffset.Now;

Well, the only thing left to do is create our desired geofence and add it to GeofenceMonitor.


            geofence = new Geofence(GeofenceKey, geocircle, GeoFenceStates, singleUse, dwellTime, GeoFenceStartTime, GeoFenceDuration);
            
            //Add the geofence to the GeofenceMonitor
            GeofenceMonitor.Current.Geofences.Add(geofence);

Now, that’s how you create your own geofence and add it to the GeofenceMonitor. Now you might wonder that whether you’d really have to define all that parameters to create a geofence. Not actually, the littlest you can do is define an Id and a Geocircle to start your geofence. 😉 The rest of the values would take the default assumption.

Handling GeoFence Notifications on Foreground:

We have all our background work to create a geofence but we wont be able to do a single thing unless we test our geofence. Now, we have already defined that our geofence would trigger events after the aforementioned dwellTime and will trigger events if I enter or leave it. So, I definitely have to attach a event handler at a certain place. Don’t I?

Before that, let’s create the method stub for the click event handler for CreateGeoFencingButton and start SetupGeofence() method inside it. If you don’t know how to do that, select the CreateGeoFencingButton in XAML, go to properties, select events tab and double click on the click textbox.


private void CreateGeoFencingButton_Click(object sender, RoutedEventArgs e)
{
SetupGeofence();
}

Then let’s add the handler in the end of SetupGeofence()


GeofenceMonitor.Current.GeofenceStateChanged += Current_GeofenceStateChanged;

Now, let’s say we want to show a message every time I enter and exit my room’s geofence. The handler might look like the following:

        private async void Current_GeofenceStateChanged(GeofenceMonitor sender, object args)
        {
            var Reports = sender.ReadReports();

            await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =&gt;
            {
                foreach (GeofenceStateChangeReport report in Reports)
                {
                    GeofenceState state = report.NewState;

                    Geofence geofence = report.Geofence;

                    if (state == GeofenceState.Entered)
                    {
                        ShowMessage(&quot;You are pretty close to your room&quot;);

                    }
                    else if (state == GeofenceState.Exited)
                    {

                        ShowMessage(&quot;You have left pretty far away from your room&quot;);
                    }
                }
            });
        }

There you go! That’s how you set up your geofence in an app running in the foreground.

Setting up GeoFence on the background:

Now, this is where things get a little bit tricky. There’s a number of steps involved in this.

  1. Create a Windows Runtime Component Project and add it to your solution.
  2. Change Package.appxmanifest to declare the BackgroundTask that has been created.
  3. Register the BackgroundTask
  4. Handle Geofence Notifications from Background Task

Create a Windows Runtime Component Project:

Usually, background tasks are windows runtime component so you have to add one to your solution. Please go over to your solution and add a Windows Runtime Project.

GeoFencing - 3

GeoFencing - 4

After the new project is created go over class1.cs and rename it to your liking . I renamed it to BackgroundTask and added IBackgroundTask interface to the class and implemented it. I didn’t write anything afterwards. Let’s just keep it like that for a while and move to our GeofenceTest Project. Go over references and   add the newly created GeofenceTask.BackgroundGeofenceTask project to it. So our Wp8.1 project now has reference to the GeofenceTask.BackgroundGeofenceTask project.

Change Package.appxmanifest to declare the BackgroundTask:

Now let’s scoot over to our Package.appxmanifest file and go over Declarations tab. From Available Declarations combobox select BackgroundTask and select loction under the Properties list.

GeoFencing - 5

Now on the Entry point field please put the full qualified assembly name of your newly created background task. Don’t get confused. It’s fairly easy. Let’s have a look at BackgroundGeofenceTask class first.

namespace GeofenceTask
{
    public sealed class BackgroundGeofenceTask : IBackgroundTask
    {
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            throw new NotImplementedException();
        }
    }
}

Now put the name as (namespace.classname) format so that leaves us with GeofenceTask.BackgroundGeofenceTask

GeoFencing - 6

Register the BackgroundTask:

Now comes the part where you register the BackgroundTask. We need to register the background task to the app so it knows it to invoke it on time.  The registering method looks like following:

private async Task RegisterBackgroundTask()
        {
            BackgroundAccessStatus backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();

            var geofenceTaskBuilder = new BackgroundTaskBuilder
            {
                Name = &quot;My Home Geofence&quot;,
                TaskEntryPoint = &quot;GeofenceTask.BackgroundGeofenceTask&quot;
            };

            var trigger = new LocationTrigger(LocationTriggerType.Geofence);
            geofenceTaskBuilder.SetTrigger(trigger);

            var geofenceTask = geofenceTaskBuilder.Register();
            geofenceTask.Completed += GeofenceTask_Completed;

            switch (backgroundAccessStatus)
            {
                case BackgroundAccessStatus.Unspecified:
                case BackgroundAccessStatus.Denied:
                    ShowMessage(&quot;This application is denied of the background task &quot;);
                    break;
            }

        }

Let’s see what we have in here now. The very first one is get the BackgroundAccessStatus. That helps us to know whether our application is capable of accessing BackgroundTasks. Now, let’s move up and use BackgroundTaskBuilder to create the background task we intend to create. Now, if you look at the TaskEntryPoint we provided there, you’d now realize why we created our Background Task project before and added it to the manifest. Because we are using the same entry point name here. I put a name to identify the background task. This is needed as if there is another background task with the same name you would be thrown an exception. If you want to know whether there is another BackgroundTask with the same name you can iterate through BackgroundTaskRegistration.AllTasks and then make sure whether there is one with the same name or not. You can use a method like the following to do so:

        public static bool IsTaskRegistered(string TaskName)
        {
            var Registered = false;
            var entry = BackgroundTaskRegistration.AllTasks.FirstOrDefault(keyval =&gt; keyval.Value.Name == TaskName);

            if (entry.Value != null)
                Registered = true;

            return Registered;
        }

I haven’t used that in this solution but feel free to definitely use this. You can even unregister to make sure that your Background Task is unregistered to open up places for others

        public static void Unregister(string TaskName)
        {
            var entry = BackgroundTaskRegistration.AllTasks.FirstOrDefault(keyval =&gt; keyval.Value.Name == TaskName);

            if (entry.Value != null)
                entry.Value.Unregister(true);
        }

The next thing that comes off is defining the LocationTrigger for the BackgroundTaskBuilder object. So, we defined a new LocationTrigger of type LocationTriggerType.Geofence and used SetTrigger method to set it up. Then we used BackgroundTaskBuilder object to register the task and we instantiated a GeofenceTask_Completed event handler for that too.

At the bottom you’d see a switch with backgroundAccessStatus and putting a MessageDialog when it’s denied or unspecified.

Handle Geofence Notifications from Background Task:

So, lets move to our Windows Runtime Component which actually is the Background Task project and implement the IBackgroundTask interface. A method named

public void Run(IBackgroundTaskInstance taskInstance)

would pop up, we’d put our regular geofence event handling in there like there in the Foreground example. Now it looks like following when we are handling it from background

    public sealed class BackgroundGeofenceTask : IBackgroundTask
    {
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            var Reports = GeofenceMonitor.Current.ReadReports();
            var SelectedReport =
                Reports.FirstOrDefault(report =&gt; (report.Geofence.Id == &quot;My Home Geofence&quot;) &amp;&amp; (report.NewState == GeofenceState.Entered || report.NewState == GeofenceState.Exited));

            if (SelectedReport==null)
            {
                return;
            }

            //We are creating a toast this time as this is running in Background
            var ToastContent = ToastNotificationManager.GetTemplateContent(ToastTemplateType.ToastText02);

            var TextNodes = ToastContent.GetElementsByTagName(&quot;text&quot;);

            if (SelectedReport.NewState == GeofenceState.Entered)
            {
                TextNodes[0].AppendChild(ToastContent.CreateTextNode(&quot;You are pretty close to your room&quot;));
                TextNodes[1].AppendChild(ToastContent.CreateTextNode(SelectedReport.Geofence.Id));
            }
            else if(SelectedReport.NewState == GeofenceState.Exited)
            {
                TextNodes[0].AppendChild(ToastContent.CreateTextNode(&quot;You are pretty close to your room&quot;));
                TextNodes[1].AppendChild(ToastContent.CreateTextNode(SelectedReport.Geofence.Id));
            }

            var settings = ApplicationData.Current.LocalSettings;

            if (settings.Values.ContainsKey(&quot;Status&quot;))
            {
                settings.Values[&quot;Status&quot;] = SelectedReport.NewState;
            }
            else
            {
                settings.Values.Add(new KeyValuePair&lt;string, object&gt;(&quot;Status&quot;, SelectedReport.NewState.ToString()));
            }

            var Toast = new ToastNotification(ToastContent);
            var ToastNotifier = ToastNotificationManager.CreateToastNotifier();
            ToastNotifier.Show(Toast);

        }
    }

Now, this looks a wee bit different from the first example. The first change that is noticable is that we are now selecting the reports based on our geofence id and the report’s new state. As we are in background now, we are using our geofence id to get the proper geofence from the whole list. And as now we are in background we are using a Toast Notification instead of a MessageDialog to show our notification.

Handling it from the App Side:

Now you guys might get confused what to do with the foreground code we made earlier. Do we need Current_GeofenceStateChanged event handler anymore. Now here we might have to be a bit careful. Now if we want our app to react different when it is on foreground and make some UI changes it needed then we have to use GeofenceTask_Completed event rather than Current_GeofenceStateChanged. And there’s another thing to be added. We get our GeofenceMonitor Reports using  GeofenceMonitor.Current.ReadReports() and this step can only be done once for every change. So if your background reads it first then, your foreground app would not be able to read it. So, we have to save it somewhere when the background reads it so our foreground app can read it from there.

So we are using ApplicationData.Current.LocalSettings to save our state in the Background Task. If you look closely you’d find the following snippet:


            var settings = ApplicationData.Current.LocalSettings;

            if (settings.Values.ContainsKey(&quot;Status&quot;))
            {
                settings.Values[&quot;Status&quot;] = SelectedReport.NewState;
            }
            else
            {
                settings.Values.Add(new KeyValuePair&lt;string, object&gt;(&quot;Status&quot;, SelectedReport.NewState.ToString()));
            }

So, in our app side GeofenceTask_Completed event handler we’d read the status and fill up a new textblock.

Thus we added a new set of textblocks in the MainPage.xaml


&lt;TextBlock Grid.Row=&quot;2&quot; Text=&quot;Status&quot; FontSize=&quot;25&quot;/&gt;
&lt;TextBlock Grid.Row=&quot;2&quot; Grid.Column=&quot;1&quot; Name=&quot;Status&quot;  FontSize=&quot;25&quot;/&gt;

Now, our GeofenceTask_Completed event handler looks like the following:

        private async void GeofenceTask_Completed(BackgroundTaskRegistration sender, BackgroundTaskCompletedEventArgs args)
        {
            if (sender != null)
            {
                // Update the UI with progress reported by the background task
                await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =&gt;
                {
                    try
                    {
                        // If the background task threw an exception, display the exception
                        args.CheckResult();

                        var settings = ApplicationData.Current.LocalSettings;

                        // get status
                        if (settings.Values.ContainsKey(&quot;Status&quot;))
                        {
                            Status.Text = settings.Values[&quot;Status&quot;].ToString();
                        }

                    }
                    catch (Exception ex)
                    {
                        ShowMessage(ex.Message);
                    }
                });
            }

        }

Now, if you look closely you will see all we did here is get the “Status” object from our ApplicationData.Current.LocalSettings and posted it on the TextBlock named Status. 🙂

Now, all we have left to do is do a little change in UI and add an extra button to set up the Geofence background task. Now it looks like the following:

GeoFencing - 8

I created the method stub for the new buttons click event too and it looks like the following:

        private async void CreateBackgroundServiceButton_Click(object sender, RoutedEventArgs e)
        {
            if (IsTaskRegistered(&quot;My Home Geofence&quot;))
            {
                Unregister(&quot;My Home Geofence&quot;);
            }
            await RegisterBackgroundTask();
        }

Testing the App on the Emulator:

You can definitely test the app on the emulator. Like always click the debug button with a emulator selected as the device and when it opens go to additional tools button and open up the location tab. Select a close location to your geofence, I did select a close one to my room and the status changed itself to “Entered”. It was that easy! You can even try the foreground example in the same way!

GeoFencing - 7

The source code is here.

Stay frosty! Hope this would help.

Windows Phones For Newbies – Tracking location in Windows Phone 8.1

Windows Phone 8.1 comes with a lot of prospects in the geo location end and usually the next thing after detecting your very own location, people tends to look for one another thing and that is tracking the location as it should update itself. So, if you’re wondering about how you should instantiate a map and track your location, you really should check out my previous post .

And if you have already done that (I hope you liked it). Then you’d probably know how to do the following:

  1. Please go ahead to your visual studio (Im using a Visual Studio 2013 Community Edition)  and open a new project on Blank App on Windows Phone 8.1
  2. Go over your project properties and go over Capabilities. Enable Location for your app (If you are from Windows Phone 8, you’d be pretty amazed that you don’t see ID_CAP_MAP anymore.

 

A Basic UI:

Let’s set up a basic UI and yes It’s kind of a rip off from MSDN but as long as it helps people, it’s cool. Our little UI has two Buttons and a number of textblocks and it looks like below in XAML (I’m only posting the main grid):


<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid.RowDefinitions>
<RowDefinition></RowDefinition>
<RowDefinition></RowDefinition>
<RowDefinition></RowDefinition>
<RowDefinition></RowDefinition>
</Grid.RowDefinitions>

<Grid>
<TextBlock Text="Location Tracker" Margin=" 15" FontSize="45"></TextBlock>
</Grid>

<Grid Grid.Row="1">
<Grid.ColumnDefinitions>
<ColumnDefinition></ColumnDefinition>
<ColumnDefinition></ColumnDefinition>
</Grid.ColumnDefinitions>
<Button Grid.Column="0" Content="Track Location" Click="TrackLocationButton_Click"
HorizontalAlignment="Center" x:Name="TrackLocationButton"
VerticalAlignment="Bottom" />

<Button IsEnabled="False" Grid.Column="1" Content="Stop Tracking" Click="StoptrackingButton_Click"
HorizontalAlignment="Center"  x:Name="StoptrackingButton"
VerticalAlignment="Bottom" />
</Grid>

<Grid Grid.Row="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="3.5*"></ColumnDefinition>
<ColumnDefinition Width="7*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<StackPanel Margin="10">
<TextBlock Text="Latitude"  FontSize="23" />
<TextBlock  Text="Longitude"  FontSize="23" />
<TextBlock  Text="Accuracy"  FontSize="23" />
</StackPanel>
<StackPanel Margin="10" Grid.Column="1">
<TextBlock  Name="LatitudeText" FontSize="23" />
<TextBlock   Name="LongitudeText" FontSize="23" />
<TextBlock   Name="AccuracyText" FontSize="23" />
</StackPanel>
</Grid>

</Grid>

If that seems a bit too much xaml for you then calm down because It looks extremely basic too:

Tracking - 1

Now, let’s move towards the MainPage.xaml.cs part. As the previous article suggests, the first thing you need is definitely a Geolocator . So please go ahead and define a Geolocator instance.


private Geolocator locator = null;

Now that we have a geo locator we can move ahead and go over the Properties of TrackLocationButton and create the method stub for Click event. And the event handler looks like below:


private void TrackLocationButton_Click(object sender, RoutedEventArgs e)
        {
            if (locator == null)
            {
                locator = new Geolocator();
            }
            if (locator != null)
            {
                locator.MovementThreshold = 3;

                locator.PositionChanged +=
                    new TypedEventHandler<Geolocator,
                        PositionChangedEventArgs>(locator_PositionChanged);

                
            }

            TrackLocationButton.IsEnabled = false;
            StoptrackingButton.IsEnabled = true;

        }

Now, if you dive a little bit into that, you will see that if the locator is instantiated then the first property we do change is the MovementThreshold property. It is the property that defines the movement threshold for the geo tracking to notify you. It’s defined in meters and thus we have defined it to 3 meters. Now next question that comes along is how would I know that I have moved my MovementThreshold amount of distance. The common answer would be actually invoking a PositionChanged event and attach a handler to it. And the handler locator_PositionChanged looks like below:


async private void locator_PositionChanged(Geolocator sender, PositionChangedEventArgs e)
{
await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
Geoposition geoPosition = e.Position;
LatitudeText.Text = geoPosition.Coordinate.Point.Position.Latitude.ToString();
LongitudeText.Text = geoPosition.Coordinate.Point.Position.Longitude.ToString();
AccuracyText.Text = geoPosition.Coordinate.Accuracy.ToString();
});
}

Now even before describing whats being done here you might wonder where the dispatcher comes from, truth is it has been declared before as:


private Geolocator locator = null;
private CoreDispatcher dispatcher;

public MainPage()
{
this.InitializeComponent();
dispatcher = Window.Current.CoreWindow.Dispatcher;
}

The reason we are using that would be pretty clear if we look at what are we doing. We are constantly updating our LatitudeText, LongitudeText, AccuracyText and as we are accessing a UI thread frequently from a event handler, we do need to make it sure it doesn’t block the regular UI interactions. Thus we used a CoreDispatcher here, much like it was in Windows Phone 8 as Dispatcher. You’d also be able to notice that the event handler is async and thus dispatcher.RunAsync invocation was awaited. We used CoreDispatcherPriority.Normal and you can even try a higher priority if you like. All this event handler is doing is it is actually updating the UI and the textblocks.

Now all you need is a StoptrackingButton to get things to stop and all you have to do is unhook the locator_PositionChanged event handler.


private void StoptrackingButton_Click(object sender, RoutedEventArgs e)
{
if (locator != null)
{
locator.PositionChanged -= new TypedEventHandler<Geolocator, PositionChangedEventArgs>(locator_PositionChanged);
}

StoptrackingButton.IsEnabled = false;
TrackLocationButton.IsEnabled = true;
}

Debugging it on the emulator:

As this sample has geolocator usage, this is always better to be tested in a device but you can definitely try it on an emulator too. To test it load the app on the emulator first by invoking build.

Tracking - 2

When the emulator hooks up open up the emulator tools and go to the location tab and click on the map to give you a primary location first. You can have a look at the gif below for an idea

Tracking - 3

Now after you pointed a primary location in the map. Now you can try clicking the track location button. After you do that Latitude, Longitude and Accuracy would pop up for the place you clicked on the map. Now click some more around it. And you will see the data changes on the textblocks.  You can do one thing more too. You can change the interaction mode from Live to Pin and play all the pins. That would even allow to emulate place changes in your emulator.  The following gif would definitely help you.

Tracking - 4

And the code sample is here.

Stay Frosty!

 

 

Different Operators in C#

In this article we will discuss about common operators that used in C#. Like any other programming languages C# has also some common operators. We can divide those as the following –
• Assignment Operator (=)
• Arithmetic Operators (+,-,*,/,%)
• Comparison Operators (==,!=,>,>=,<,<=)
• Conditional Operators (&&,||)
• Ternary Operator (?:)
• Null Coalescing Operator (??)
Now we will discuss about each of this operator in details.

Assignment Operator (=)

This is a very common operator in every programming language. It is used to assign a value in a variable. We can give a variable a value by this operator. Suppose we declare a variable by the following instruction-

Int variable_name;

Then this variable reserve some memory in RAM but no value is saved in those memory. We can assign value to those memory by using assignment operator as follows-

Int variable_name=5;

Now the value 5 is reserved in those memory blocks. So assignment operator is used to assign values.

Arithmetic Operators (+,-,*,/,%)

These operators are used to perform arithmetic operation. In many places of a program we need to perform many arithmetic operation. So it is important to understand these operators closely.
The “+” operator performs addition operation. Suppose we want to add two values. Then we can do that by the following-

Int a = 5+4;
Or,
Int a=5;
Int b=6;
Int result= a+b;

The “+” operator takes two operands and return the result of addition between those operands. Similarly “-” operator performs the subtraction operation between two operands. It will subtract its right side operand from left side operand and return the result. The multiplication operator is “*”. It will perform multiplication operation.
Now the two operator / and % is related to division operation. The forward slash (/) operator returns the quotient of the division operation and “%” (read as MOD) operator returns the reminder. To understand the difference we consider a division operation. Suppose we want to divide 10 by 2. So here the Quotient will be 5 and reminder will be 0. If we use / operator then it will return 5 and if we use % then it will return 0. Consider the following program-

using System;
class Program
{
   static void Main()
    {
        int Numerator = 10;
        int Denominator = 2;

        int result = Numerator / Denominator;

        Console.WriteLine("{0}", result);
    }
}

The above program will print 5 because here we use / operator and it will return quotient. If we used % in place of / then it will print the reminder that is 0 here.

Comparison Operators (==,!=,>,>=,<,<=)

Comparison operators are used to compare to value and always return true or false. Every comparison operator has a meaning and performs a specific compare operation. The best example of this operator is in conditional statement. The statement in which we compare something in respect with some condition is called conditional statement. There are some keywords that used in conditional statement, one of this is “if” keyword. It is very common in almost all programming languages.
The double equal sign is used to compare equality. Consider the following example-

using System;
class Program
{
   static void Main()
    {
        int a = 10;
       if(a==10)
       {
           Console.WriteLine("{0}", a);
       }
        
    }
} 

In the above example we compare the value of variable with 10. If the value of variable a is equal to 10 then the next instruction will execute. The next instruction is to print the value of ‘a’ that is 10 here. So the program will print 10.
The “!=” operator is used to check inequality. For example in the above example we can check the variable ‘a’ is not equal or not. If we want to execute another instruction if the variable is not equal to 10 then code should be as follows-

using System;
class Program
{
   static void Main()
    {
        int a = 5;
       if(a==10)
       {
           Console.WriteLine("{0}", a);
       }
       if(a!=10)
       {
           Console.WriteLine("a is not equal to 10");
       }
    }
}

The above program will print “a is not equal to 10” because the value of a is 5 here. The != operator used here to execute the meaningful string that user can understand specifically that a is not equal to 10.
Similarly we can check greater than relation by the “>” operator. It will return true if the right side operand is greater than the left side operand. If we want to check greater or equal relation then we can use >= operator. It will return true if the left side operand is greater than right side operand and also if the operands are equal to each other.
Like greater than relation we can check less than relation by “<” operator and less than or equal relation by “<=” operator.

Conditional Operators (&&,||)

There are two operators that used in conditional statements named as AND (&&) and OR (||). If there is any situation where we need to execute a statement if and only if some of conditions are true then we can use && operator. This operator takes two condition and execute next instructions if all of those conditions are true. Suppose we have to check if a number is less than 5 and greater than 1 or not then we can check it by && operator as following-

using System;
class Program
{
   static void Main()
    {
        int a=2;
        
       if(a1 )
       {
           Console.WriteLine("a is less than 5 and greater than 1");
       }
        
    }
}

In the above example two conditions is checked, one is a is less than 5 and the other is a is greater than 1. So the print instruction will be executed if each of these instruction are true. Another operator is || (OR) this operator used as the same of && operator but if any one of the condition is true between two then the next instruction will execute. The OR operator return true if any one of the condition is true. In the above example if we used OR operator then weather the value of a is less than 5 or greater than 1 the print instruction will execute.

 
using System;
class Program
{
   static void Main()
    {
        int a=10;
        
       if(a1 )
       {
           Console.WriteLine("a is less than 5 OR greater than 1");
       }
        
    }
}

In the above example the condition a is less than 5 is false but a is greater than 1 true, so one of the condition is true. That’s why the print instruction will execute.

Ternary Operator (?:)

The ternary operator is a very interesting operator. It gives us two options if any condition is true than do something otherwise do something. The syntax of ternary operator can be written as follows-
Any Condition ? do if the condition is true : do if condition is false
We can see it by the following code-

using System;
class Program
{
   static void Main()
    {
        int a=10;
        bool ISValue10 = a == 10 ? true : false;

        Console.WriteLine("{0}", ISValue10);
        
    }
}

In the above example the condition is if the variable “a” is equal to 10 or not. If it is true then the bool type variable “ISValue10” will be assigned by true otherwise false. Here the example will print true because here the value of variable is 10. We can do the same by if statement but it will take more instruction that we have done here with one instruction. That is the benefit of using ternary operator.

Null Coalescing Operator (??)

To understand null coalescing operator first we have to understand nullable types in C#. Actually we can divide the types in C# in two broad categories-
• Value types
• Reference types
In the previous article we have already seen the value types and those are- integer, double, float, decimal etc. We have also seen a reference type that is string type. String is actually a class. We will discuss about reference types and value types in details in the later session. What we need to understand at this point is types in C# can be divided in two broad categories that is value type and reference type. Example of value type is integer, float, double, structs, enums and example of reference type is interface, delegates, arrays, class etc. And another point we need to keep in mind at this point is the default value of a reference type is null and the default value for value type is some form of zero. For example the default value of type integer is zero and it cannot hold the value null. To assign null in a variable we use the keyword null in C#. If we try to assign null to a integer type variable then we will get an error. So value type cannot hold null value. But as I told before that string is a class that is reference type so we can assign a string variable with null. For an example we can write-

 
string s = null;

but we cannot write-

int a = null; 

If we try to assign null to a integer type variable then it will return an immediate error. Sometimes it is necessary to assign a value types variable with the value null. Generally it is necessary if we use C# to communicate with a database. Since nullable types and non-nullable types is not a concept of database it is a concept of C#, any of the field in a database can be null. Sometimes for making decision it is necessary to assign null to value type variable. Again we get here two types, one is nullable and the other is non-nullable. We can assign null to non-nullable types by using the ? operator.
Suppose we have a form that ask the user a question “Are you a teacher?” and this field is optional. User can say yes or no and the user can also keep the field empty. If we have a bool type variable to store the answer then we can assign true or false in this variable nothing else. But if the user keep the field empty we need to assign null to bool type variable. We can do it by using ? operator as follows.

bool? ISUserTeacher = null;

So we can make a non-nullable type a nullable type by using ? operator. Now consider an example to understand null coalescing operator. Suppose a have 10 mangoes in a tree and we store the result in a integer type variable as follows-

int MangoesInTree = 10; 

Now it is possible that there is no mangoes in the tree. So we have to make the integer variable a nullable variable that we can assign null value to it. We can do it as follows-

int? MangoesInTree = null; 

Suppose we have another variable named availablemangoes and we will assign the value of MangoesInTree in it if MangoesInTree is not null. If MangoesInTree is null then we will assign 0 to availablemangoes variable. We can do it as follows-

using System;
class Program
{
   static void Main()
    {
        int? MangoesInTree = null;

        int availablemangoes;

       if(MangoesInTree==null)
       {
           availablemangoes = 0;
       }
       else
       {
           availablemangoes = MangoesInTree;
       }
	Console.WriteLine(“{0}”,availablemangoes);
    }
}

Unfortunately we will get an error here that “cannot imlicitly convert type int? to int”. Here MangoesInTree variable is a nullable variable but availablemangoes is not a nullable variable so it cannot be assigned by the nullable types. Here we can use a way to do it. It is called type casting. We will discuss about type casting and implicit, explicit type conversion in the very next article. So just for now note it, we can do the above program as follows-

using System;
class Program
{
   static void Main()
    {
        int? MangoesInTree = null;

        int availablemangoes;

       if(MangoesInTree==null)
       {
           availablemangoes = 0;
       }
       else
       {
           availablemangoes = (int)MangoesInTree;
       }
Console.WriteLine(“{0}”,availablemangoes);

    }
} 

Now it will print the value of availablemangoes as we wanted. But we can do the same program with just one line and this is what the null coalescing operator is. We can do the same program with null coalescing operator. The above program with null coalescing operator can be written as follows-

using System;
class Program
{
   static void Main()
    {
        int? MangoesInTree = 10;

        int availablemangoes;

        availablemangoes = MangoesInTree ?? 0;

       Console.WriteLine("{0}", availablemangoes);
    }
}

Look closely to the above program here we do the same thing with just one line of code. Here the default value what we want to assign in non-nullable variable is given after the null coalescing operator (??) and before the operator we supply the value that we want to assign if the MangoesInTree variable is not null that is the variable itself. That is the purpose of null coalescing operator. It helps to assign a non-nullable types with nullable types in C#.

Reading and Writing to the Console

In the previous article we discussed about the basic structure of a C# program. Today we will see reading and writing operation to the console. We will see a little more interactive sample program than the previous today. Our program will ask the user his/her name and then print a welcome message with the name of the user which he/she just enter.

To write something to the console we have two methods under System namespace, one is Write and the other is WriteLine. Only the difference between these two is, if we use WriteLine then after writing something to the console it will print a new line also but in Write method it will just print something. No new line will be printed here.

For an example if we write in the main method Console.Write(“Hello World ”); then the output should be as follows-

Hello World press any key to continue

The line “press any key to continue” indicates that the program is terminated. Instead of this method if we use Console.WriteLine(“Hello World ”); then the output should be as follows-

Hello World

press any key to continue

Here we can see that the line “press any key to continue” is in a new line. So the method Writeline prints a new line after writing something to the console.

Similarly there are to methods for reading something in the console, one is Read and the other is ReadLine. The Read method read integer type from the console and the Readline method read string type from the console. So if we write Console.ReadLine() then we have to store the returned result in a string type variable so that we can use it later in the program.

Now let’s see the code our sample program. It is as follows-

using System;
class Program
{
   static void Main()
    {
        Console.WriteLine("What is your name?");
        string name = Console.ReadLine();
        Console.WriteLine("Welcome "+ name);
    }
}

Here we can see in the MAIN method first we are printing a message asking the user’s name. Then when our next line of code executed it waits for the user input that is our read operation from the console. When the user enters something and press the Enter button then Console.Readline methos reads what is entered in the console and return it as a string type. Here we store the returned string in a string type variable named name. So what user entered in the console now stored in the variable. Then in the next line we write in the console “Welcome “concatenated with the name of the user. Here we are concatenating two string- One is “Welcome ” and the other is string type variable called name with the “+” sign in the WriteLine method.
There are actually two ways of writing something in the console. They are-
• Concatenation
• Place holder syntax
We already have seen the concatenation method of writing something to the console. Now we will see the place holder syntax in the same program. If we want to use place holder syntax in the same program then the code should be as follows-

using System;
class Program
{
   static void Main()
    {
        Console.WriteLine("What is your name?");
        string name = Console.ReadLine();
        Console.WriteLine("Welcome {0}",name);
    }
}

Here we can see in case of “+” operator we use “{0}” in the string with Welcome. This is called the place holder. When we run the program, the value of the variables that we pass after comma in the WriteLine method replaces the place holder. So if we run this piece of code we will see the same result here.
The place holder syntax is more preferable than the Concatenation process. To see how place holder syntax gives more capability let’s modify the above program. Now we will ask the user to enter his/her first name then after reading the first name we will ask for last name and after reading that we will print the first name and last name separated by a comma with the welcome message. To do that the program should be as follows –

using System;
class Program
{
   static void Main()
    {
        Console.WriteLine("What is your first name?");
        string firstname = Console.ReadLine();
        Console.WriteLine("What is your last name?");
        string lastname = Console.ReadLine();
        Console.WriteLine("Welcome {0},{1}",firstname,lastname);
    }
}

Here in the code we can see there are two place holders and there are two string type variable as well to store the first name and last name of user. When we write the welcome message in WriteLine method we use two placeholder and two variable to replace the place holder. In the same way we can use as many as place holders we required. We just have to surround the number of that place holder with curly braces. That’s why place holder syntax is more preferable than the concatenation method.

Saving a SpeechSynthesis Audio in a windows store/phone app

Usually after doing a little speech synthesizing in our phone we usually stumble on one question, can I save this stream?
Luckily you can! All you gotta do is pull this out of your sleeve. 🙂

 


var synth = Windows.Media.SpeechSynthesis.SpeechSynthesizer();

SpeechSynthesisStream speechstream = await synth.SynthesizeTextToStreamAsync("Hello People");

using(var reader = new DataReader(speechstream))
{

await reader.LoadAsync((uint)stream.Size);

IBuffer buffer = reader.ReadBuffer((uint)stream.Size);

await FileIO.WriteBufferAsync(outputFile, buffer);

}

And, you’re done! Your file would be a .wav file of course.