Repository Pattern with Windows Azure Mobile Services for Windows Phone app and Windows Store app

Windows Azure Mobile Services is a fantastic tool and very easy to use. In this post I will show you how to use the repository pattern with the Mobile Services SDK.

If you are familiar with Entity Framework, this pattern is used in many projects and samples. You can find a definition here http://msdn.microsoft.com/en-us/library/ff649690.aspx or here http://www.codeproject.com/Articles/526874/Repositorypluspattern-2cplusdoneplusright

In this sample, we will use the portable library to share our data access layer with Windows Phone, Windows 8 and .net apps.

At the end, we will be able to inject our repository in our services / view models and to make our code testable.

MyNamespace.Models

public class ToDoItem
{
        public int Id { get; set; }
        public string Title { get; set; }
        public string Description { get; set; }
}

MyNamespace.Data

public interface IRepository<T>
{
        Task<IEnumerable<T>> GetAllAsync();
        Task CreateAsync(T entity);
        Task UpdateAsync(T entity);
        Task RemoveAsync(T entity);
}

public interface IToDoItemRepository : IRepository<ToDoItem>
{
 
}

MyNamespace.Data.MobileService

public abstract class BaseRepository<TEntity> : IRepository<TEntity> where TEntity : class
{
        protected IMobileServiceClient MobileServiceClient { get; set; }
 
        protected BaseRepository(IMobileServiceClient mobileServiceClient)
        {
            if (mobileServiceClient == null) throw new ArgumentNullException("mobileServiceClient");
            this.MobileServiceClient = mobileServiceClient;
        }
 
        protected virtual IMobileServiceTable<TEntity> GetTable()
        {
            return this.MobileServiceClient.GetTable<TEntity>();
        }
 
        public virtual Task<IEnumerable<TEntity>> GetAllAsync()
        {
            return GetTable().ToEnumerableAsync();
        }
        public virtual Task CreateAsync(TEntity entity)
        {
            return GetTable().InsertAsync(entity);
        }
 
        public virtual Task<IEnumerable<TEntity>> FindAsync(Expression<Func<TEntity, bool>> predicate)
        {
            return GetTable().Where(predicate).ToEnumerableAsync();
        }
 
        public virtual Task UpdateAsync(TEntity entity)
        {
            return GetTable().UpdateAsync(entity);
        }
        public virtual Task RemoveAsync(TEntity entity)
        {
            return GetTable().DeleteAsync(entity);
        }
}

public class ToDoItemRepository : BaseRepository<ToDoItem>, IToDoItemRepository
{
        public ToDoItemRepository(IMobileServiceClient mobileServiceClient) : base(mobileServiceClient)
        {
        }
}

How to use my repository?

public class Bootstrapper : AutofacBootstrapper
{
        protected override void ConfigureContainer(ContainerBuilder builder)
        {
            // register MobileServiceClient
            builder.RegisterType<MobileServiceClient>()
                .AsImplementedInterfaces()
                .WithParameter("applicationUrl", "MyAppUrl")
                .WithParameter("applicationKey", "MyAppKey")
                .InstancePerLifetimeScope();
 
            // register ToDoItemRepository
            builder.RegisterType<ToDoItemRepository>().AsImplementedInterfaces().InstancePerLifetimeScope();
 
            base.ConfigureContainer(builder);
        }
}

public class MainViewModel : Screen
{
        private readonly IToDoItemRepository _toDoItemRepository;
        private List<ToDoItem> _toDoItems;
 
        public MainViewModel(IToDoItemRepository toDoItemRepository)
        {
            _toDoItemRepository = toDoItemRepository;
        }
 
        protected override void OnActivate()
        {
            LoadData();
        }
 
        private async void LoadData()
        {
            // create an entry for the test
            await _toDoItemRepository.CreateAsync(new ToDoItem {Title = "my title", Description = "my description"});
 
            // load all data
            ToDoItems = new List<ToDoItem>(await _toDoItemRepository.GetAllAsync());
        }
 
        public List<ToDoItem> ToDoItems
        {
            get { return _toDoItems; }
            set
            {
                if (Equals(value, _toDoItems)) return;
                _toDoItems = value;
                NotifyOfPropertyChange(() => ToDoItems);
            }
        }
}

Source code: Mahalo.MobileServiceRepositoryPattern.7z (5,48 mb)

Autofac and Quartz.NET

Quartz.NET is an open source project for job scheduling and is a port of popular open source Java job scheduling framework.

If you usually used DI in your project, you should want to used it the job. To do that with Autofac, you have to create your own factory.

At first, create the class AutofacJobFactory:

public class AutofacJobFactory : IJobFactory
{
    private readonly IContainer _container;

    public AutofacJobFactory(IContainer container)
    {
        if (container == null) throw new ArgumentNullException("container");
        _container = container;
    }

    public IJob NewJob(TriggerFiredBundle bundle, IScheduler scheduler)
    {
        return (IJob)_container.Resolve(bundle.JobDetail.JobType);
    }
}

 And now, you can configure Quartz to use AutofacJobFactory to create their jobs.

string mySchedulerCronExpression  = ConfigurationManager.AppSettings["MySchedulerCronExpression"];
IContainer = container = InitializeDependencyInjectionContainer();
                
var schedulerFactory = new StdSchedulerFactory();
var scheduler = schedulerFactory.GetScheduler();
scheduler.JobFactory = new AutofacJobFactory(container);
scheduler.Start();

IJobDetail job = JobBuilder.Create<MyJob>().WithIdentity("MyJob").Build();
ITrigger trigger =
    TriggerBuilder.Create()
                    .WithIdentity("MyJobTrigger")
                    .WithCronSchedule(mySchedulerCronExpression)
                    .Build();

scheduler.ScheduleJob(job, trigger);

And voila :) Your job are now injected via Autofac !

Edinburgh Airport app for Windows Store

I'm currently working on a new app for Windows 8: Edinburgh Airport. This app is not official and I develop it because I often need to know some stuff like the flight infos...

My app is not yet available in the store but I hope to release it very soon.

I already make some screenshot.

MyNes for Windows 8

After a couple of month of working on my new project, I'm proud to show you the first video of MyNes, a NES emulator for Windows 8.

Microsoft Language Portal

For all my applications, I develop specific version for many languages. Until now, I used google / bing translate. I found today a great site from Microsoft to translate specic terms from their dictionaries which are used in their products !

http://www.microsoft.com/Language/en-US/Search.aspx?sString=start+page&langID=fr-FR

Thank MS !

Navigation with Caliburn.Micro for WinRT

Caliburn.Micro for WinRT provides a full implementation of the MVVM pattern for the Windows 8 apps. The approach of a standard app is the pattern ViewFirst. This means, that you have to give the complete url of a new page to navigate.

With Caliburn.Micro you have the ViewModel first approach. With that, it's very easier to navigate from a viewModel to an other. The purpose of this post is to show you how to pass a parameter between 2 pages, so 2 viewModels.

Here a code sample :

public class ViewModel1:Screen
{
    private readonly INavigationService _navigationService;

    // Injection of the navigation service
    public ViewModel1(INavigationService navigationService)
    {
        _navigationService = navigationService;
    }

    // Command from a button click event
    public void NavigateCommand()
    {
        string parameter = "value";
        // call NavigateToViewModel from the navigation serice
        _navigationService.NavigateToViewModel<ViewModel2>(parameter);
    }
}

public class ViewModel2 : Screen
{
    // The property should be named Parameter
    public string Parameter { get; set; }
}

Hope this helps :)

Add a separator line in a XAML AppBar

Unfortunately, XAML doesn’t provide an AppBarCommand separator control like there is in JavaScript.

To add a separator you could use a simple XAML Line element.

<Line X1="0" Y1="60"  Margin="0,10,0,0"  StrokeThickness="3" Stroke="White"></Line>

UrlEncode & HtmlEncode in WinRT

If your are looking HttpUtility in WinRT, you will search for a while :) All helpers to encode/decode Url / Html are now availbale int he namespace System.Net.WebUtility.

System.Net.WebUtility.HtmlDecode(string);
System.Net.WebUtility.HtmlEncode(string);
System.Net.WebUtility.UrlEncode(string);
System.Net.WebUtility.UrlDecode(string);

Hope this help !

Handle global keyboard events in WinRT

I was searching for a global way to handle the KeyDown or KeyUp event for an entire Page in a Modern UI app.

Fortunately, I found a nice thing, it's possible to handle the KeyDown/KeyUp event for the whole page by subscribing to the events:

Window.Current.CoreWindow.KeyDown += CoreWindow_KeyDown;

Window.Current.CoreWindow.KeyUp += CoreWindow_KeyUp;

This is also very useful for my new game :)

Cryptography in WinRT

The new cryptography API in WinRT is not very easy, specially if you know the .net API...

Here a small code to show how to use the APIs !

using Windows.Security.Cryptography;
using Windows.Security.Cryptography.Core;
using Windows.Storage.Streams;

namespace SampleHashAlgorithmProvider
{

    sealed partial class HashAlgProviderApp : Application
    {
        public HashAlgProviderApp()
        {
            // Initialize the application.
            this.InitializeComponent();

            // Hash a message.
            String strAlgName = HashAlgorithmNames.Sha512;
            String strMsg = "This is a message to be hashed.";
            String strEncodedHash = this.SampleHashMsg(strAlgName, strMsg);
        }

        public String SampleHashMsg(String strAlgName, String strMsg)
        {
            // Convert the message string to binary data.
            IBuffer buffUtf8Msg = CryptographicBuffer.ConvertStringToBinary(strMsg, BinaryStringEncoding.Utf8);

            // Create a HashAlgorithmProvider object.
            HashAlgorithmProvider objAlgProv = HashAlgorithmProvider.OpenAlgorithm(strAlgName);

            // Demonstrate how to retrieve the name of the hashing algorithm.
            String strAlgNameUsed = objAlgProv.AlgorithmName;

            // Hash the message.
            IBuffer buffHash = objAlgProv.HashData(buffUtf8Msg);

            // Verify that the hash length equals the length specified for the algorithm.
            if (buffHash.Length != objAlgProv.HashLength)
            {
                throw new Exception("There was an error creating the hash");
            }

            // Convert the hash to a string (for display).
            String strHashBase64 = CryptographicBuffer.EncodeToBase64String(buffHash);

            // Return the encoded string
            return strHashBase64;
        }
    }
}