C#

UserData.xaml.cs
        private async void SaveDataButton_Click(object sender, RoutedEventArgs e)
        {
            StorageFile userFile = await KnownFolders.PicturesLibrary.CreateFileAsync("userdata.txt", CreationCollisionOption.ReplaceExisting);
            await FileIO.WriteTextAsync(userFile, UserDataTextBox.Text);
        }
 
        private async void GetDataButton_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                StorageFile userFile = await KnownFolders.PicturesLibrary.GetFileAsync("userdata.txt");
                StoredData.Text = await FileIO.ReadTextAsync(userFile);
            }
            catch
            {
                throw new Exception("Data not found!");
            }
        }

VB

UserData.xaml.vb
Private Async Sub SaveDataButton_Click(sender As Object, e As RoutedEventArgs)
    Dim userFile As StorageFile =
        Await KnownFolders.PicturesLibrary.CreateFileAsync("userdata.txt",
                                                           CreationCollisionOption.ReplaceExisting)
    Await FileIO.WriteTextAsync(userFile, UserDataTextBox.Text)
End Sub
 
Private Async Sub GetDataButton_Click(sender As Object, e As RoutedEventArgs)
    Try
        Dim userFile As StorageFile = Await KnownFolders.PicturesLibrary.GetFileAsync("userdata.txt")
        StoredData.Text = Await FileIO.ReadTextAsync(userFile)
    Catch
        Throw New Exception("Data not found!")
    End Try
End Sub

Starting in Windows 8.1 it is also possible to use another class to retrieve all libraries folders: StorageLibrary. With this object you can easily handle your libraries thanks to integration with the FilePicker object.

C#

UserData.xaml.cs
public async void GetFile()
{
    FileOpenPicker openPicker = new FileOpenPicker();
    openPicker.ViewMode = PickerViewMode.List;
    openPicker.SuggestedStartLocation = PickerLocationId.Desktop;
    openPicker.FileTypeFilter.Add(".txt");
    StorageFile file = await openPicker.PickSingleFileAsync();
 
    if (file != null)
    {
        //do something
    }
}
 
UserData.xaml.cs
public async void GetFolder()
{
    FolderPicker openPicker = new FolderPicker();
    openPicker.ViewMode = PickerViewMode.List;
    openPicker.SuggestedStartLocation = PickerLocationId.Desktop;
    openPicker.FileTypeFilter.Add(".txt");
    StorageFolder folder = await openPicker.PickSingleFolderAsync();
 
    if (folder != null)
    {
        //do something
    }
}

VB

UserData.xaml.vb
Public Async Sub GetFile()
    Dim openPicker As New FileOpenPicker()
    openPicker.ViewMode = PickerViewMode.List
    openPicker.SuggestedStartLocation = PickerLocationId.Desktop
    openPicker.FileTypeFilter.Add(".txt")
    Dim file As StorageFile = Await openPicker.PickSingleFileAsync()
    
    If file IsNot Nothing Then
        'do something
    End If
End Sub
 
UserData.xaml.vb
Public Async Sub GetFolder()
    Dim openPicker As New FolderPicker()
    openPicker.ViewMode = PickerViewMode.List
    openPicker.SuggestedStartLocation = PickerLocationId.Desktop
    openPicker.FileTypeFilter.Add(".txt")
    Dim folder As StorageFolder = Await openPicker.PickSingleFolderAsync()
 
    If folder IsNot Nothing Then
          'do something
    End If
End Sub

If you need to save a file to a location, you need to use the FileSavePicker. Once the window is opened by calling the PickSaveFileAsync() method, the user can type a name or leave the default file name set using the SuggestedFileName property. It is also possible to set the following:

• The default folder using the SuggestedStartLocation property
• The default extension using the DefaultFileExtension property

Then the user confirms the saving of the file and PickSaveFileAsync() returns a StorageFile object that is the saved file. Remember that it is possible to share your files in other applications by integrating the file picker contracts.

C#

SQLiteHelper.cs
public async static void CreateDatabase()
{
    var storagePath = Windows.Storage.ApplicationData.Current.LocalFolder;
    var file = await storagePath.TryGetItemAsync("db.sqlite");
 
    if (file == null)
    {
        var dbPath = System.IO.Path.Combine(
            Windows.Storage.ApplicationData.Current.LocalFolder.Path, "db.sqlite");
 
        try
        {
            using (var db = new SQLiteConnection(dbPath))
            {
                db.CreateTable<SimpleAppointment>();
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
}
 
public static void AddAppointment(SimpleAppointment appointment)
{
    var dbPath = System.IO.Path.Combine(
        Windows.Storage.ApplicationData.Current.LocalFolder.Path, "db.sqlite");
 
    try
    {
        using (var db = new SQLiteConnection(dbPath))
        {
            db.RunInTransaction(() =>
                    {
                        db.Insert(new SimpleAppointment()
                        {
                            Id = appointment.Id,
                            Subject = appointment.Subject,
                            Location = appointment.Location,
                            StartDate = appointment.StartDate,
                            EndDate = appointment.EndDate
                        });
                    }
            );
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}
 
public static SimpleAppointment GetAppointment(int id)
{
    var dbPath = System.IO.Path.Combine(
        Windows.Storage.ApplicationData.Current.LocalFolder.Path, "db.sqlite");
 
    try
    {
        using (var db = new SQLiteConnection(dbPath))
        {
            return db.Find<SimpleAppointment>(id);
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}
 
SQLiteAccess.xaml.cs
private void SaveButton_Click(object sender, RoutedEventArgs e)
{
    SQLiteHelper.AddAppointment(new SimpleAppointment
                                    {
                                        Subject = SubjectTextBox.Text,
                                        Location = LocationTextBox.Text,
                                        StartDate = StartDatePicker.Date.Date,
                                        EndDate = EndDatePicker.Date.Date
                                    });
 
    ResultTextBlock.Text = "Appointment saved!";
 
}
 
private void ClearButton_Click(object sender, RoutedEventArgs e)
{
    SubjectTextBox.Text = String.Empty;
    LocationTextBox.Text = String.Empty;
    StartDatePicker.Date = DateTime.Now;
    EndDatePicker.Date = DateTime.Now;
}
 
private void LoadButton_Click(object sender, RoutedEventArgs e)
{
    SimpleAppointment appointment = SQLiteHelper.GetAppointment(1);
 
    SubjectTextBox.Text = appointment.Subject;
    LocationTextBox.Text = appointment.Location;
    StartDatePicker.Date = appointment.StartDate;
    EndDatePicker.Date = appointment.EndDate;
}
 
 
public SQLiteAccess()
{
    this.InitializeComponent();
    this.navigationHelper = new NavigationHelper(this);
 
    //Create a SQLite database if not exists
    SQLiteHelper.CreateDatabase();
}
 
SimpleAppointment.cs
public class SimpleAppointment
{
    [SQLite.PrimaryKey]
    [SQLite.AutoIncrement]
    public int Id { get; set; }
    public string Subject { get; set; }
    public string Location { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
}

After adding a reference to SQLite in your project, a file named SQLite.cs is added. This file is a wrapper that helps you use SQLite. Unfortunately, there’s no official wrapper for SQLite to use with languages other than C#. But there are unofficial wrappers like Visual Basic Sqlite WinRT Wrapper (code.msdn.microsoft.com/windowsapps/Visual-Basic-Sqlite-WinRT-bf6fe131).

There is another good way to use the official library inside your project via a language other than C#. You just need to create a DLL (or WinRT component) and then add it to your project. A good explanation from Tim Heuer is at timheuer.com/blog/archive/2012/08/07/updated-how-to-using-sqlite-from-windows-store-apps.aspx.

Finally, to explore SQLite data inside your db, you can use a tool like SQLite Browser: sourceforge.net/projects/sqlitebrowser.

C#

FakeServiceClient.cs
namespace Win8Organizer.CSharp.Model.FakeServiceReference
{
    public partial class FakeServiceClient :
        System.ServiceModel.ClientBase<Win8Organizer.Csharp.Model.FakeServiceReference.IfakeService>,
            Win8Organizer.Csharp.Model.FakeServiceReference.IfakeService
    {
        static partial void ConfigureEndpoint(System.ServiceModel.Description.ServiceEndpoint serviceEndpoint,
            System.ServiceModel.Description.ClientCredentials clientCredentials)
        {
            if (serviceEndpoint.Name ==
                FakeServiceReference.FakeServiceClient
                    .EndpointConfiguration.BasicHttpBinding_IfakeService.ToString())
            {
                serviceEndpoint.Binding.SendTimeout = new System.TimeSpan(0, 1, 0);
            }
        }
    }
}

VB

Partial Public Class FakeServiceClient
    Inherits System.ServiceModel.ClientBase(Of FakeServiceReference.IFakeService)
    Implements FakeServiceReference.IFakeService
 
    Partial Private Shared Sub ConfigureEndpoint(ByVal serviceEndpoint As System.ServiceModel.Description.ServiceEndpoint,
                                                 ByVal clientCredentials As System.ServiceModel.Description.ClientCredentials)
        ' Implementation is moved after the FakeServiceClient instantiation
        ' because partial method must have empty body
    End Sub
 
    Public Function GetSimpleAppointmentAsync() As Task(Of FakeServiceReference.SimpleAppointment)
                                Implements FakeServiceReference.IFakeService.GetSimpleAppointmentAsync
        Return MyBase.Channel.GetSimpleAppointmentAsync
    End Function
End Class

Now that you’ve configured the service reference, you are ready to create a proxy class and retrieve data inside your application. Let’s see how to add your app to a WCF Service to get appointments information.

First, take a look at the FakeService.svc:

C#

IFakeService.cs
    [ServiceContract]
    public interface IFakeService
    {
 
        [OperationContract]
        SimpleAppointment GetSimpleAppointment();
    }
 
 
    // Use a data contract as illustrated in the sample below to add composite types to service operations.
    [DataContract]
    public class SimpleAppointment
    {
        [DataMember]
        public int Id { get; set; }
 
        [DataMember]
        public string Subject { get; set; }
 
        [DataMember]
        public string Location { get; set; }
 
        [DataMember]
        public DateTime StartDate { get; set; }
 
        [DataMember]
        public DateTime EndDate { get; set; }
    }
 
FakeService.svc.cs
public class FakeService : IFakeService
{
    SimpleAppointment IFakeService.GetSimpleAppointment()
    {
        return new SimpleAppointment()
        {
            Id = 1,
            Subject = "New Appointment",
            Location = "12, Kennedy Street, Washington",
            StartDate = DateTime.Now,
            EndDate = DateTime.Now.AddDays(1)
        };
    }
}

In Figure 8-18 you saw how to add reference to the FakeService. Now let’s see how to call the web service. Remember: web service calls must be asynchronous!

C#

WCFClient.xaml.cs
private async void LoadButton_Click(object sender, RoutedEventArgs e)
{
    try
    {
        FakeServiceReference.FakeServiceClient svc = new FakeServiceReference.FakeServiceClient();
 
        FakeServiceReference.SimpleAppointment appointment = await svc.GetSimpleAppointmentAsync();
 
        SubjectTextBox.Text = appointment.Subject;
        LocationTextBox.Text = appointment.Location;
        StartDatePicker.Date = appointment.StartDate;
        EndDatePicker.Date = appointment.EndDate;
    }
    catch
    {
        ResultTextBlock.Text = "Oops! Something went wrong!";
    }
}

VB

Private Async Sub LoadButton_Click(sender As Object, e As RoutedEventArgs)
    Try
        Dim svc As New FakeServiceReference.FakeServiceClient
 
        If svc.Endpoint.Name = FakeServiceReference.FakeServiceClient.EndpointConfiguration.BasicHttpBinding_IFakeService.ToString() Then
            svc.Endpoint.Binding.SendTimeout = New System.TimeSpan(0, 1, 0)
        End If
 
        Dim appointment As FakeServiceReference.SimpleAppointment = Await svc.GetSimpleAppointmentAsync()
 
        SubjectTextBox.Text = appointment.Subject
        LocationTextBox.Text = appointment.Location
        StartDatePicker.[Date] = appointment.StartDate
        EndDatePicker.[Date] = appointment.EndDate
    Catch
        ResultTextBlock.Text = "Oops! Something went wrong!"
    End Try
End Sub

WinRT provides also the SyndicationApi. It is a set of classes that helps retrieve feeds from the Web. The usage is very simple: the class SyndicationClient performs the whole process, starting a connection, reading the feed, and returning a list of SyndicationItem:

C#

RssHelper.cs
public async static Task<string> GetFeedTitleAsync()
{
    string response = String.Empty;
    SyndicationFeed feed = new SyndicationFeed();
    SyndicationClient client = new SyndicationClient();
 
    try
    {
        feed = await client.RetrieveFeedAsync(
            new Uri("http://www.apress.com/index.php/dailydeals/index/rss"));
 
        response = feed.GetXmlDocument(SyndicationFormat.Rss20).GetXml();
    }
    catch (Exception ex)
    {
        SyndicationErrorStatus status = SyndicationError.GetStatus(ex.HResult);
        if (status == SyndicationErrorStatus.InvalidXml)
        {
            response += "Invalid XML!";
        }
 
        if (status == SyndicationErrorStatus.Unknown)
        {
            response = ex.Message;
        }
    }
 
    return response;
}

VB

RSSHelper.vb
Public NotInheritable Class RssHelper
    Private Sub New()
    End Sub
    Public Shared Async Function GetFeedTitleAsync() As Task(Of String)
        Dim response As String = [String].Empty
        Dim feed As New SyndicationFeed()
        Dim client As New SyndicationClient()
 
        Try
            feed = Await client.RetrieveFeedAsync(New Uri("http://www.apress.com/index.php/dailydeals/index/rss"))
 
            response = feed.GetXmlDocument(SyndicationFormat.Rss20).GetXml()
        Catch ex As Exception
            Dim status As SyndicationErrorStatus = SyndicationError.GetStatus(ex.HResult)
            If status = SyndicationErrorStatus.InvalidXml Then
                response += "Invalid XML!"
            End If
 
            If status = SyndicationErrorStatus.Unknown Then
                response = ex.Message
            End If
        End Try
 
        Return response
    End Function
End Class

Starting with Windows 8.1 there is new namespace to handle HTTP web requests and REST web services: Windows.Web.Http. Inside this namespace you can find several helpful objects to achieve simple or complex tasks related to the Web. The features include the following:

• Handling HTTP common verbs (DELETE, GET, PUT and POST)
• Support for common authentication settings and patterns
• Support for SSL
• Customized filters
• Full support for cookies
• Asynchronous operations

The main class is HTTPClient and it allows you to send and receive requests over the HTTP protocol. Using the filtering mechanism, it is possible to customize the request based on the scenario:

C#

HTTPClient.xaml.cs
private async void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
    // TODO: Create an appropriate data model for your problem domain to replace the sample data
    var item = await SampleDataSource.GetItemAsync((String)e.NavigationParameter);
    //this.DefaultViewModel["Item"] = item;
 
    ResultTextBlock.Text = await
        new HttpClient().GetStringAsync(
            new Uri("http://www.apress.com/index.php/dailydeals/index/rss"
            )
        );
}

VB

HTTPClient.xaml.vb
Private Async Sub NavigationHelper_LoadState(sender As Object, e As Common.LoadStateEventArgs)
    ' TODO: Create an appropriate data model for your problem domain to replace the sample data
    Dim item As Data.SampleDataItem = Await Data.SampleDataSource.GetItemAsync(DirectCast(e.NavigationParameter, String))
    Me.DefaultViewModel("Item") = item
 
    ResultTextBlock.Text = Await New HttpClient().
        GetStringAsync(New Uri("http://www.apress.com/index.php/dailydeals/index/rss"))
End Sub

C#

public static Microsoft.WindowsAzure.MobileServices.MobileServiceClient
    buildingwindows8appsfromthegroundupmobileserviceClient =
    new Microsoft.WindowsAzure.MobileServices.MobileServiceClient(
"https://buildingwindows8appsfromthegroundupmobileservice.azure-mobile.net/",
"YOUR_APP_KEY");

VB

Public Shared bw8agu_mobileserviceClient As New Microsoft.WindowsAzure.MobileServices.MobileServiceClient(
"https://buildingwindows8appsfromthegroundupmobileservice.azure-mobile.net/",
"YOUR_APP_KEY")

This key can be retrieved in the Windows Azure Mobile Services dashboard via the “Connect an existing Windows Store app” item (Figure 8-32).

Here is how to execute some basic operations on the table behind the Windows Azure Mobile Service just created:

C#

public static class AzureMobileServicesHelper
{
    public async static void InsertDataFromAzureMobileSvc(SimpleAppointment item)
    {
        await App.bw8agu_mobileserviceClient.GetTable<SimpleAppointment>()
            .InsertAsync(item);
    }
 
    public async static Task<MobileServiceCollection<SimpleAppointment, SimpleAppointment>> GetDataFromAzureMobileSvc()
    {
        try
        {
            IMobileServiceTable<SimpleAppointment> table =
                App.bw8agu_mobileserviceClient
                .GetTable<SimpleAppointment>();
 
            return await table.ToCollectionAsync<SimpleAppointment>();
        }
        catch (Exception ex)
        { throw ex; }
    }
 
    public static void UpdateDataFromAzureMobileSvc(SimpleAppointment item)
    {
        try
        {
            IMobileServiceTable<SimpleAppointment> table = App.bw8agu_mobileserviceClient.GetTable<SimpleAppointment>();
 
            table.UpdateAsync(item);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
}

VB

Public NotInheritable Class AzureMobileServicesHelper
    Private Sub New()
    End Sub
    Public Shared Async Sub InsertDataFromAzureMobileSvc(item As SimpleAppointment)
        Await App.bw8agu_mobileserviceClient.GetTable(Of SimpleAppointment)().InsertAsync(item)
    End Sub
 
    Public Shared Async Function GetDataFromAzureMobileSvc() As Task
                As Task(Of MobileServiceCollection(Of SimpleAppointment, SimpleAppointment))
        Try
            Dim table As IMobileServiceTable(Of SimpleAppointment) =
                App.bw8agu_mobileserviceClient.GetTable(Of SimpleAppointment)()
 
            Return Await table.ToCollectionAsync()
        Catch ex As Exception
            Throw ex
        End Try
    End Function
 
    Public Shared Async Sub UpdateDataFromAzureMobileSvc(item As SimpleAppointment)
        Try
            Dim table As IMobileServiceTable(Of SimpleAppointment) =
                App.bw8agu_mobileserviceClient.GetTable(Of SimpleAppointment)()
 
            Await table.UpdateAsync(item)
        Catch ex As Exception
            Throw ex
        End Try
    End Sub
End Class

The following code can be used to call one of these operations.

C#

AzureMobileServices.xaml.cs
private void SaveButton_Click(object sender, RoutedEventArgs e)
{
    try
    {
        AzureMobileServicesHelper.InsertDataFromAzureMobileSvc(new SimpleAppointment
                                        {
                                            Subject = SubjectTextBox.Text,
                                            Location = LocationTextBox.Text,
                                            StartDate = StartDatePicker.Date.Date,
                                            EndDate = EndDatePicker.Date.Date
                                        });
 
        ResultTextBlock.Text = "Appointment saved!";
    }
    catch (Exception ex)
    {
        ResultTextBlock.Text = ex.Message;
    }
 
}
 
private void ClearButton_Click(object sender, RoutedEventArgs e)
{
    SubjectTextBox.Text = String.Empty;
    LocationTextBox.Text = String.Empty;
    StartDatePicker.Date = DateTime.Now;
    EndDatePicker.Date = DateTime.Now;
}
 
private async void LoadButton_Click(object sender, RoutedEventArgs e)
{
    SimpleAppointment appointment = (await AzureMobileServicesHelper.GetDataFromAzureMobileSvc()).FirstOrDefault();
 
    SubjectTextBox.Text = appointment.Subject;
    LocationTextBox.Text = appointment.Location;
    StartDatePicker.Date = appointment.StartDate;
    EndDatePicker.Date = appointment.EndDate;
}

VB

AzureMobileServices.xaml.vb
Private Sub SaveButton_Click(sender As Object, e As RoutedEventArgs)
    Try
        AzureMobileServicesHelper.InsertDataFromAzureMobileSvc(New SimpleAppointment() With { _
             .Subject = SubjectTextBox.Text, _
             .Location = LocationTextBox.Text, _
             .StartDate = StartDatePicker.[Date].[Date], _
             .EndDate = EndDatePicker.[Date].[Date] _
        })
 
        ResultTextBlock.Text = "Appointment saved!"
    Catch ex As Exception
        ResultTextBlock.Text = ex.Message
    End Try
End Sub
 
Private Sub ClearButton_Click(sender As Object, e As RoutedEventArgs)
    SubjectTextBox.Text = [String].Empty
    LocationTextBox.Text = [String].Empty
    StartDatePicker.[Date] = DateTime.Now
    EndDatePicker.[Date] = DateTime.Now
End Sub
 
Private Async Sub LoadButton_Click(sender As Object, e As RoutedEventArgs)
    Dim appointment As SimpleAppointment = (
        Await AzureMobileServicesHelper.GetDataFromAzureMobileSvc()).FirstOrDefault()
    SubjectTextBox.Text = appointment.Subject
    LocationTextBox.Text = appointment.Location
    StartDatePicker.[Date] = appointment.StartDate
    EndDatePicker.[Date] = appointment.EndDate
End Sub

Data just inserted can be showed in the Mobile Services panel on the portal in the used table inside the Data section (Figure 8-33).

Last but not least, the Windows Azure Mobile Services portal is a simple and useful environment to check the state and the usage of your services. Indeed, the dashboard shows a chart containing all the API calls, CPU times, and data out info (Figure 8-34). You can also manage notification, scalability, and authentication.

C#

PasswordVault.xaml.cs
private void LoginButton_Click(object sender, RoutedEventArgs e)
{
    if (PasswordVaultHelper.CheckPassword(UsernameTextBox.Text, PasswordTextBox.Password))
    {
        ResultTextBlock.Text = "Login succeeded!";
    }
    else
    {
        ResultTextBlock.Text = "Login failed!";
    }
    ClearTextboxes();
}
 
private void SaveButton_Click(object sender, RoutedEventArgs e)
{
    PasswordVaultHelper.SavePasswordToVault(UsernameTextBox.Text, PasswordTextBox.Password);
 
    ResultTextBlock.Text = "Credentials saved!";
    ClearTextboxes();
}
 
private void ClearButton_Click(object sender, RoutedEventArgs e)
{
    ClearTextboxes();
    ResultTextBlock.Text = String.Empty;
}
 
private void ClearTextboxes()
{
    UsernameTextBox.Text = String.Empty;
    PasswordTextBox.Password = String.Empty;
}
 
PasswordVaultHelper.cs
public class PasswordVaultHelper
{
    private static PasswordVault vault =
        new Windows.Security.Credentials.PasswordVault();
 
    public static IList<PasswordCredential> LoadPasswordVault()
    {
        //Load all credentials
        IReadOnlyList<PasswordCredential> creds = vault.RetrieveAll();
 
        return creds.ToList<PasswordCredential>();
    }
 
    public static bool CheckPassword(string username, string password)
    {
        bool res = false;
 
        try
        {
            IReadOnlyList<PasswordCredential> creds = vault.FindAllByUserName(username);
 
            foreach (PasswordCredential cred in creds)
            {
                cred.RetrievePassword();
                res = cred.Password == password;
            }
        }
        catch
        {
            //do nothing
        }
 
        return res;
    }
 
    public static void SavePasswordToVault(string username, string password)
    {
        LoadPasswordVault();
 
        PasswordCredential cred = new PasswordCredential("BW8AGU", username, password);
 
        vault.Add(cred);
    }
}

VB

PasswordVault.xaml.vb
Private Sub LoginButton_Click(sender As Object, e As RoutedEventArgs)
    If PasswordVaultHelper.CheckPassword(UsernameTextBox.Text, PasswordTextBox.Password) Then
        ResultTextBlock.Text = "Login succeeded!"
    Else
        ResultTextBlock.Text = "Login failed!"
    End If
    ClearTextboxes()
End Sub
 
Private Sub SaveButton_Click(sender As Object, e As RoutedEventArgs)
    PasswordVaultHelper.SavePasswordToVault(UsernameTextBox.Text, PasswordTextBox.Password)
 
    ResultTextBlock.Text = "Credentials saved!"
    ClearTextboxes()
End Sub
 
Private Sub ClearButton_Click(sender As Object, e As RoutedEventArgs)
    ClearTextboxes()
    ResultTextBlock.Text = [String].Empty
End Sub
 
Private Sub ClearTextboxes()
    UsernameTextBox.Text = [String].Empty
    PasswordTextBox.Password = [String].Empty
End Sub

PasswordVaultHelper.vb
Public Class PasswordVaultHelper
    Private Shared vault As PasswordVault = New Windows.Security.Credentials.PasswordVault()
 
    Public Shared Function LoadPasswordVault() As IList(Of PasswordCredential)
        'Load all credentials
        Dim creds As IReadOnlyList(Of PasswordCredential) = vault.RetrieveAll()
 
        Return creds.ToList()
    End Function
 
    Public Shared Function CheckPassword(username As String, password As String) As Boolean
        Dim res As Boolean = False
 
        Try
            Dim creds As IReadOnlyList(Of PasswordCredential) = vault.FindAllByUserName(username)
 
            For Each cred As PasswordCredential In creds
                cred.RetrievePassword()
                res = cred.Password = password
            Next
            'do nothing
        Catch
        End Try
 
        Return res
    End Function
 
    Public Shared Sub SavePasswordToVault(username As String, password As String)
        LoadPasswordVault()
 
        Dim cred As New PasswordCredential("BW8AGU", username, password)
 
        vault.Add(cred)
    End Sub
End Class

The Credential Locker also allows you to store multiple credentials, and it’s possible to set a default one using the Default property in the PasswordCredential.Properties collection. Besides, you can share credentials across apps using the ApplicationSuiteId property.

C#

public static class FacebookHelper
{
    private const string _appID = "<your_app_id>";  //retrieved from Facebook app page
    private const string _url = "https://www.facebook.com/connect/login_success.html";
    private const string _wallUrl = "https://graph.facebook.com/<your_facebook_username>/feed";
    private static string _accessToken = String.Empty;
    private static string _urlAccessToken = String.Empty;
 
    public static async Task<bool> Authenticate()
    {
        bool res = false;
 
        try
        {
            String FacebookURL = "https://www.facebook.com/dialog/oauth?client_id=" +
                Uri.EscapeDataString(_appID) +
                "&redirect_uri=" + Uri.EscapeDataString(_url) +
                "&scope=read_stream,user_about_me,read_stream," +
                "publish_stream&display=popup&response_type=token";
 
            System.Uri requestUri = new Uri(FacebookURL);
            System.Uri callbackUri = new Uri(_url);
 
            WebAuthenticationResult WebAuthenticationResult =
                await WebAuthenticationBroker.AuthenticateAsync(
                                        WebAuthenticationOptions.None,
                                        requestUri,
                                        callbackUri);
 
            if (WebAuthenticationResult.ResponseStatus ==
                WebAuthenticationStatus.Success)
            {
                _urlAccessToken = WebAuthenticationResult.ResponseData.ToString();
                _accessToken = _urlAccessToken.Substring(_urlAccessToken.IndexOf('=') + 1);
            }
            else if (WebAuthenticationResult.ResponseStatus ==
                WebAuthenticationStatus.ErrorHttp)
            {
                throw new Exception("HTTP Error: " +
                    WebAuthenticationResult.ResponseErrorDetail.ToString());
            }
            else
            {
                throw new Exception("Error: " +
                    WebAuthenticationResult.ResponseStatus.ToString());
            }
 
            res = true;
        }
        catch (Exception Error)
        {
            //log the error somewhere
        }
 
        return res;
    }
 
    public static async Task<string> PostOnFacebook(string text)
    {
        string res = String.Empty;
 
        try
        {
            var client = new HttpClient();
 
            // Create the HttpContent for the form to be posted.
            var requestContent = new FormUrlEncodedContent(new[] {
                    new KeyValuePair<string, string>("message", text)
                });
 
            // Get the response.
            HttpResponseMessage response = await client.PostAsync(
                "https://graph.facebook.com/<your_facebook_username>/feed?access_token=" + _accessToken,
                requestContent);
 
            // Get the response content.
            HttpContent responseContent = response.Content;
 
            // Get the stream of the content.
            using (var reader = new StreamReader(await responseContent.ReadAsStreamAsync()))
            {
                // Write the output.
                res = reader.ReadToEnd();
            }
        }
        catch (Exception ex)
        {
            //log the error somewhere
            res = ex.Message;
        }
 
        return res;
    }
}
 
FacebookAuth.xaml.cs
private async void Authenticate()
{
    bool res = await FacebookHelper.Authenticate();
 
    if (!res)
    {
        ResultTextBlock.Text = "Something went wrong!";
    }
}
 
private void PostButton_Click(object sender, RoutedEventArgs e)
{
    Authenticate();
 
    PostIt();
}
 
private async void PostIt()
{
    ResultTextBlock.Text = await FacebookHelper.PostOnFacebook(MessageTextBox.Text);
}

VB

FacebookHelper.vb
Public NotInheritable Class FacebookHelper
    Private Sub New()
    End Sub
    Private Const _appID As String = "<your_app_id>"
    'retrieved from Facebook app page
    Private Const _url As String = "https://www.facebook.com/connect/login_success.html"
    Private Const _wallUrl As String = "https://graph.facebook.com/<your_facebook_username>/feed"
    Private Shared _accessToken As String = [String].Empty
    Private Shared _urlAccessToken As String = [String].Empty
 
    Public Shared Async Function Authenticate() As Task(Of Boolean)
        Dim res As Boolean = False
 
        Try
            Dim FacebookURL As [String] = "https://www.facebook.com/dialog/oauth?client_id=" +
                Uri.EscapeDataString(_appID) + "&redirect_uri=" + Uri.EscapeDataString(_url) +
                "&scope=read_stream,user_about_me,read_stream," +
                "publish_stream&display=popup&response_type=token"
 
            Dim requestUri As System.Uri = New Uri(FacebookURL)
            Dim callbackUri As System.Uri = New Uri(_url)
 
            Dim WebAuthenticationResult As WebAuthenticationResult =
                Await WebAuthenticationBroker.AuthenticateAsync(WebAuthenticationOptions.None, requestUri, callbackUri)
 
            If WebAuthenticationResult.ResponseStatus = WebAuthenticationStatus.Success Then
                _urlAccessToken = WebAuthenticationResult.ResponseData.ToString()
                _accessToken = _urlAccessToken.Substring(_urlAccessToken.IndexOf("="c) + 1)
            ElseIf WebAuthenticationResult.ResponseStatus = WebAuthenticationStatus.ErrorHttp Then
                Throw New Exception("HTTP Error: " + WebAuthenticationResult.ResponseErrorDetail.ToString())
            Else
                Throw New Exception("Error: " + WebAuthenticationResult.ResponseStatus.ToString())
            End If
 
            res = True
            'log the error somewhere
        Catch [Error] As Exception
        End Try
 
        Return res
    End Function
 
    Public Shared Async Function PostOnFacebook(text As String) As Task(Of String)
        Dim res As String = [String].Empty
 
        Try
            Dim client = New HttpClient()
 
            ' Create the HttpContent for the form to be posted.
                        Dim requestContent = New FormUrlEncodedContent(New () {
                                             New KeyValuePair(Of String, String)("message", text)})
 
            ' Get the response.
            Dim response As HttpResponseMessage = Await client.PostAsync(
Convert.ToString("https://graph.facebook.com/<your_facebook_username>/feed?access_token=") & _accessToken, requestContent)
 
            ' Get the response content.
            Dim responseContent As HttpContent = response.Content
 
            ' Get the stream of the content.
            Using reader = New StreamReader(Await responseContent.ReadAsStreamAsync())
                ' Write the output.
                res = reader.ReadToEnd()
            End Using
        Catch ex As Exception
            'log the error somewhere
            res = ex.Message
        End Try
 
        Return res
    End Function
End Class
 
FacebookAuth.xaml.vb
Private Async Sub Authenticate()
    Dim res As Boolean = Await FacebookHelper.Authenticate()
 
    If Not res Then
        ResultTextBlock.Text = "Something went wrong!"
    End If
End Sub
 
Private Sub PostButton_Click(sender As Object, e As RoutedEventArgs)
    Authenticate()
 
    PostIt()
End Sub
 
Private Async Sub PostIt()
    ResultTextBlock.Text = Await FacebookHelper.PostOnFacebook(MessageTextBox.Text)
End Sub

Calling the method Authenticate() will open up Facebook login form (Figure 8-37).

C#

ContactPicker.xaml.cs
private void ContactPickerButton_Click(object sender, RoutedEventArgs e)
{
    GetContact();
}
 
private async void GetContact()
{
    //Create a new instance of ContactPicker class
    var contactPicker = new Windows.ApplicationModel.Contacts.ContactPicker();
    contactPicker.CommitButtonText = "Select";
 
    //Set the selection mode
    contactPicker.SelectionMode = ContactSelectionMode.Fields;
 
    //Set desired fields
    contactPicker.DesiredFieldsWithContactFieldType.Add(ContactFieldType.Email);
 
    //Open the ContactPicker
    Contact contact = await contactPicker.PickContactAsync();
 
    if (contact != null)
    {
        ResultTextBlock.Text = contact.FirstName;
    }
}

VB

Private Sub ContactPickerButton_Click(sender As Object, e As RoutedEventArgs)
    GetContact()
End Sub
 
Private Async Sub GetContact()
    'Create a new instance of ContactPicker class
    Dim contactPicker = New Windows.ApplicationModel.Contacts.ContactPicker()
    contactPicker.CommitButtonText = "Select"
 
    'Set the selection mode
    contactPicker.SelectionMode = ContactSelectionMode.Fields
 
    'Set desired fields
    contactPicker.DesiredFieldsWithContactFieldType.Add(ContactFieldType.Email)
 
    'Open the ContactPicker
    Dim contact As Contact = Await contactPicker.PickContactAsync()
 
    If contact IsNot Nothing Then
        ResultTextBlock.Text = contact.FirstName
    End If
End Sub

Figure 8-39 shows an example of ContactPicker (for privacy, most parts of the image are blanked).