VB Magic

2012/10/30

Accessing and OData Feed in WinRT App using Visual Basic.NET

Filed under: .NET, VB.NET, Windows 8, Windows Store App — Tags: , , , — vbmagic @ 5:12 pm

As I’ve been searching the internet to try and find ways of accessing OData Feeds in visual basic .net and not finding much help I thought I’d put together a small example to help others.

This will use a demo OData feed to pull customer records from an example banking application. The feed is located in an Azure Cloud Service and is accessed by the following URL

http://t24irisdemo.cloudapp.net/tbank/Wealth.svc/

(This feed may be removed in the future)

The first thing to do is create a Visual Basic Blank Windows Store XAML application.

Also add a basic page called CustomerPage.

Add a Service Reference which points to the above URL

Visual Studio Dialog

Add Service Reference

We will only use Customers from the feed.

First display all the customers. To do this we need to add a Gridview to the main page XAML with an Item Template to display customer information. (I’m not a designer so I apologies for the rough look of the details 😉 )

        <GridView x:Name="defaultGridView" Grid.Row="1" Tapped="defaultGridView_Tapped_1" Margin="10" BorderBrush="#FFF7EC05" BorderThickness="1" FontFamily="Global User Interface" >
            <GridView.ItemTemplate>
                <DataTemplate>
                    <Grid Width="250" Height="135" Background="#002">
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="*" />
                            <RowDefinition Height="*" />
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="100" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <TextBlock Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="0" Text="{Binding Path=CustomerCode}" HorizontalAlignment="Center" FontWeight="ExtraBold" ></TextBlock>
                        <Image Grid.Column="0" Grid.Row="1" Grid.RowSpan="2" Source="{Binding Path=Photo}" Stretch="Uniform" Margin="4" VerticalAlignment="Center" HorizontalAlignment="Center"/>
                        <TextBlock Grid.Column="1" Grid.Row="1"  FontStyle="Italic" VerticalAlignment="Bottom">Name:</TextBlock>
                        <TextBlock Grid.Column="1" Grid.Row="2" Text="{Binding Path=Name}" VerticalAlignment="Top" HorizontalAlignment="Left" TextWrapping="Wrap"></TextBlock>
                    </Grid>
                </DataTemplate>
            </GridView.ItemTemplate>
        </GridView>

Next add the following code to the code behind for the Main Page.

Imports System.Data.Services.Client

' The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238

''' <summary>
''' An empty page that can be used on its own or navigated to within a Frame.
''' </summary>
Public NotInheritable Class MainPage
    Inherits Page

    Private Const IRISURL As String = "http://t24irisdemo.cloudapp.net/tbank/Wealth.svc"
    Private _context As New irisServiceReference.T24Wealth(New Uri(IRISURL))
    Private WithEvents _allCust As DataServiceCollection(Of irisServiceReference.Customers)

    ''' <summary>
    ''' Invoked when this page is about to be displayed in a Frame.
    ''' </summary>
    ''' <param name="e">Event data that describes how this page was reached.  The Parameter
    ''' property is typically used to configure the page.</param>
    Protected Overrides Sub OnNavigatedTo(e As Navigation.NavigationEventArgs)

        _allCust = New DataServiceCollection(Of irisServiceReference.Customers)
        AddHandler _allCust.LoadCompleted, AddressOf LoadAllCustComplete
		
		Dim query = _context.Customers
        _allCust.LoadAsync(query)
    End Sub

    Private Sub LoadAllCustComplete(sender As Object, e As LoadCompletedEventArgs)
        defaultGridView.ItemsSource = _allCust
    End Sub

    Private Sub defaultGridView_Tapped_1(sender As Object, e As TappedRoutedEventArgs)
        Dim gv As GridView = sender

        Dim item As irisServiceReference.Customers = gv.SelectedItem
        Dim customerNo As String = customerNo = item.CustomerCode

        Frame.Navigate(GetType(CustomerPage), customerNo)
    End Sub
End Class

The above code will pull all the customers from the feed and then bind them to the GridView. There is also a Tap event handler which will pull the customer number from the grid view item and navigate to the customer view page (I’ll leave this to you to have a go a designing the look and feel. In the following code example I assumed there is a text block called customerNameTextBlock).

If you put a debug point at the _allCust.LoadAsync(query) line. You will notice that Query is turned into a URL to the feed.

query = {http://t24irisdemo.cloudapp.net/tbank/Wealth.svc/Customers}

Next we need to put code behind the Customer info page to pull the tapped customer details back so that we can populate this page. The following code with do this.

' The Basic Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234237
Imports System.Data.Services.Client

''' <summary>
''' A basic page that provides characteristics common to most applications.
''' </summary>
Public NotInheritable Class CustomerPage
    Inherits Common.LayoutAwarePage

    Private Const IRISURL As String = "http://t24irisdemo.cloudapp.net/tbank/Wealth.svc"
    Private _context As New irisServiceReference.T24Wealth(New Uri(IRISURL))
    Private WithEvents _allCust As DataServiceCollection(Of irisServiceReference.Customers)

        ''' <summary>
        ''' Populates the page with content passed during navigation.  Any saved state is also
        ''' provided when recreating a page from a prior session.
        ''' </summary>
        ''' <param name="navigationParameter">The parameter value passed to
        ''' <see cref="Frame.Navigate"/> when this page was initially requested.
        ''' </param>
        ''' <param name="pageState">A dictionary of state preserved by this page during an earlier
        ''' session.  This will be null the first time a page is visited.</param>
    Protected Overrides Sub LoadState(navigationParameter As Object, pageState As Dictionary(Of String, Object))

    End Sub

        ''' <summary>
        ''' Preserves state associated with this page in case the application is suspended or the
        ''' page is discarded from the navigation cache.  Values must conform to the serialization
        ''' requirements of <see cref="Common.SuspensionManager.SessionState"/>.
        ''' </summary>
        ''' <param name="pageState">An empty dictionary to be populated with serializable state.</param>
    Protected Overrides Sub SaveState(pageState As Dictionary(Of String, Object))

    End Sub

    Protected Overrides Sub OnNavigatedTo(e As Navigation.NavigationEventArgs)
        Dim customerNo As String = e.Parameter

        pageTitle.Text = "Customer " + customerNo

        _allCust = New DataServiceCollection(Of irisServiceReference.Customers)
        AddHandler _allCust.LoadCompleted, AddressOf allCustomerLoadCompleted

        Dim query = From c In _context.Customers
                    Where c.CustomerCode = customerNo
                    Select c

        _allCust.LoadAsync(query)
    End Sub

    Private Sub allCustomerLoadCompleted(sender As Object, e As LoadCompletedEventArgs)
        customerNameTextBlock.Text = _allCust.Single.Name
    End Sub

End Class

You’ll notice in this piece of code that a Linq query is used to pull the customer record from the feed. If you again put a debug point at _allCust.LoadAsync(query) you will notice the query is also transformed into a OData URL.

query = {http://t24irisdemo.cloudapp.net/tbank/Wealth.svc/Customers()?$filter=CustomerCode eq '100320'}

Hopefully this very simple example will help you get kick-started in developing WinRT applications that access OData feed.

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