Building and Deploying Applications for Windows Azure : Creating a Demo Project

10/10/2010 3:32:31 PM
Creating applications for Windows Azure is something that affects a big plethora of scenarios, because you can generally build and deploy any kind of Web applications. This article provides an example of a Silverlight Web application to show how different technologies (ASP.NET, Silverlight, and Azure) can coexist in the cloud development. With that said, run Visual Studio 2010 and open the New Project dialog.

Visual Studio Requires Elevated Privileges

To test your Windows Azure applications locally, Visual Studio needs to be run with elevated privileges (Run as Administrator). This is required because Visual Studio needs to launch the Development Fabric, which also needs to be run with elevated privileges.

Click the Cloud Service folder and select the Windows Azure Cloud Service project template. Name the new project as AzureBookstore. See Figure 1 for details.

Figure 1. Creating the new project.

After you click OK, another dialog displays requesting you to specify the application type. In this dialog select the ASP.NET Web Role option and press the right arrow so that everything appears as in Figure 2.

Figure 2. Selecting the project type.

It is possible to select different kinds of projects, such as ASP.NET MVC 2 or WCF projects. The ASP.NET Web Role is the most common template for classic ASP.NET applications. After this, Visual Studio generates a new solution storing two projects: The first project is the Cloud service that stores information for the Windows Azure hosting service. The second project is the ASP.NET Web application that you actually work on. Before putting hands on the code, an explanation about both projects is required.

Understanding Web Roles and Web Configuration

A key concept in Windows Azure development is the role, which is typically a single component running in the Azure environment and built in managed code. Roles can be of two types: web roles and worker roles. A Web role is generally an ASP.NET Web application, like the case of our sample scenario. As you may remember from Figure 2, additional Web roles are available for WCF and FastCGI applications. You may instead think of worker roles as of services running behind the scenes, like in the case of Windows services, in the cloud. An Azure project can have multiple roles and multiple instances of one role; moreover, you can configure roles as required. When you create new Cloud projects, the new solution will contain a Web role project (simply an ASP.NET Web project) and a service project where you can configure role properties. To access roles configuration, in Solution Explorer right-click the WebRole1 role and select Properties. At this point a special implementation of the My Project designer will pop up. Figure 3 shows what you will see on the screen.

Figure 3. Accessing role configuration options.

The Configuration tab enables first setting the .NET trust level for roles. By default the trust level is Full Trust. The Windows Azure partial trust level has instead some limitations and denies your role access to some resources, such as the Registry, isolated storage, printing, and OleDb connections. The full restrictions list is available here: The Instance Count field enables setting how many instances of the role are permitted, whereas VM Size enables specifying the size of the virtual machine hosting your service. Small means one CPU core, 1.7 gigabytes of memory, and 250 gigabytes of hard disk space. Medium means two CPU cores, 3.5 gigabytes of memory, and 500 gigabytes of hard disk space. Large means four CPU cores, 7 gigabytes of memory, and 1 terabyte of hard disk space; finally, ExtraLarge means eight CPU cores, 15 gigabytes of memory, and 2 terabytes of hard disk space. The Startup action group enables specifying if debugging should be launched via an HTTP or and HTTPS endpoint (which must be defined in the Endpoints tab). In the Settings tab you can define settings that you can access via the Windows Azure SDK Runtime API. By default each role has a DiagnosticsConnectionString that defines whether you need access to the local storage or the online services. In the Endpoints tab you can define endpoints for your application. Deciding to apply for an HTTPS endpoint also requires a valid SSL certificate. You add certificates to your deployment via the Certificates tab. Finally, the Local Storage tab enables configuring the file system storage resources local for each instance. All the preceding options and settings are reflected into the ServiceConfiguration.cscfg and ServiceDefinition.csdef files that you can see in Solution Explorer and that are basically XML representations of settings.

Adding Multiple Roles and 64-Bit Considerations

You can add multiple web roles and worker roles by right-clicking the Roles folder in Solution Explorer. Another consideration that you need to keep in mind is that Windows Azure is a 64-bit operating system, so take care of this if you plan to invoke unmanaged code that might fail.

The default role for the new project is associated with the ASP.NET project that will actually run the application. You can therefore build your application directly within the Web project or add a Silverlight project, as explained in next section.

Adding a Silverlight 3 Project

A web project can host Silverlight applications, as you may remember from previous discussions about this technology. This also true in Windows Azure scenarios. The goal of this chapter is building a Silverlight application capable of showing and editing a list of books within a DataGrid control, also providing the ability of reading and saving data to Xml taking advantage of the isolated storage. At this point right-click the web project name in Solution Explorer and click Add New Item. Notice that we are not adding a new project, but simply an item. When the Add New Item dialog appears, click the Silverlight folder on the left and select the Silverlight Application item template, naming the new item as BookStore.vbproj (see Figure 4 for details).

Figure 4. Adding a Silverlight project to the solution.

When you add the new project, a dialog asks for specifying the Silverlight version, the project path, and other information such as enabling debugging. Leave the default settings unchanged, as shown in Figure 5, and continue.

Figure 5. Setting options for the new Silverlight project.

Because we use LINQ to Xml for listing and saving books, and because this will be accomplished using a DataGrid control, add references to the System.Xml.dll, System.Xml.Linq.dll and System.Windows.Controls.Data.dll assemblies. Now there is the need of implementing a Book class representing one book and a BooksCollection class representing a typed collection of books, so add a new code file to the Silverlight project named Book.vb. Code in Listing 1 demonstrates this.

Listing 1. Implementing Classes for Representing Books
Imports System.Collections.ObjectModel

Public Class Book

Public Property Title As String
Public Property Author As String
Public Property DatePublished As Date
Public Property ISBN As String

End Class
Public Class BooksCollection
Inherits ObservableCollection(Of Book)

Public Sub New(ByVal source As IEnumerable(Of Book))
For Each b As Book In source
End Sub

Public Sub New()

End Sub
End Class

For the sake of clarity, implement just a DataGrid and a Button for saving data. The following XAML code must replace the Grid definition:

<Grid x:Name="LayoutRoot" Background="Green">
<RowDefinition Height="50"/>
<data:DataGrid Name="BooksGrid" Grid.Row="0" ItemsSource="{Binding}"
AutoGenerateColumns="True" />
<StackPanel Grid.Row="1" Orientation="Horizontal">
<Button Width="100" Height="40" Margin="5"
Content="Save" Name="SaveButton"/>

The DataGrid is defined within the System.Windows.Controls.Data namespace; because of this, you need to add the following Xml namespace declaration at page level to use it:


Now it is time to write Visual Basic code. Our goal is reading data from an Xml file containing books’ definitions and that is stored in the Silverlight’s isolated storage. If the file is not found, which is the case of the first run, an empty books collection is defined. Finally the code provides the ability of saving data to the isolated storage. Listing 2 shows all these operations (read comments within code for explanations).

Listing 2. Defining Code for Retrieving, Showing, and Saving Books Definitions
Imports System.Xml.Linq
Imports System.IO, System.Text
Imports System.IO.IsolatedStorage

Partial Public Class MainPage
Inherits UserControl

'Declaring a books collection
Private MyBooks As BooksCollection

'Required for understanding if the DataGrid
'is in edit mode
Private isEditing As Boolean = False

Public Sub New()

End Sub

'Used to generate data if the data file is not
Private Function CreateData() As BooksCollection
Dim b As New Book With {.ISBN = "0000000"}

Dim bc As New BooksCollection
Return bc
End Function

'Attempts to read the data file from the isolated storage
'If found, with a LINQ to Xml query a new books collection
'is returned. If not found, a new empty collection is
'generated and returned
Private Function GetBooks() As BooksCollection
Dim doc As XDocument

Using store As IsolatedStorageFile = IsolatedStorageFile.
Dim st As IsolatedStorageFileStream = _
store.OpenFile("Books.xml", FileMode.Open)
doc = XDocument.Load(st)
End Using

Dim query = From pbook In doc...<Book>
Select New Book With {.Author = pbook.@Author,
.Title = pbook.@Title,
.DatePublished = Date.
.ISBN = pbook.@ISBN

Return New BooksCollection(query)

Catch ex As Exception
Return CreateData()
End Try
End Function

Private Sub MainPage_Loaded(ByVal sender As Object,
ByVal e As System.Windows.
RoutedEventArgs) Handles Me.Loaded
'Populates data
Me.MyBooks = GetBooks()
'Sets data-binding
Me.DataContext = Me.MyBooks
End Sub

'Saves data to the isolated storage. The Xml data is generated
'with LINQ to Xml embedded-expressions
Private Sub SaveButton_Click(ByVal sender As System.Object,
ByVal e As System.Windows.
RoutedEventArgs) Handles SaveButton.Click
Dim data = <?xml version="1.0" encoding="utf-8"?>
<%= From b In MyBooks
Select <Book Author=<%= b.Author %>
Title=<%= b.Title %>
ISBN=<%= b.ISBN %>
DatePublished=<%= b.DatePublished.
ToString %>/>

Using store As IsolatedStorageFile = IsolatedStorageFile.
Dim st As IsolatedStorageFileStream = _
store.OpenFile("Books.xml", FileMode.Create)
End Using
End Sub
Private Sub BooksGrid_BeginningEdit(ByVal sender As Object,
ByVal e As System.Windows.Controls.
DataGridBeginningEditEventArgs) _
Handles BooksGrid.BeginningEdit
isEditing = True
End Sub

'Allows DataGrid editing
Private Sub BooksGrid_KeyDown(ByVal sender As Object,
ByVal e As System.Windows.Input.
KeyEventArgs) Handles BooksGrid.KeyDown
If isEditing = False Then
'If the user press Delete, removes the selected item
If e.Key = Key.Delete Then

If Me.BooksGrid.SelectedItem IsNot Nothing Then
Me.MyBooks.Remove(CType(Me.BooksGrid.SelectedItem, Book))
End If
'If the user press Insert, adds a new empty item to the collection
ElseIf e.Key = Key.Insert Then
Dim b As New Book With {.DatePublished = Today}
Dim index As Integer = MyBooks.IndexOf(CType(Me.BooksGrid.
SelectedItem, Book))

MyBooks.Insert(index + 1, b)
BooksGrid.SelectedIndex = index
End If
End If
End Sub

Private Sub BooksGrid_RowEditEnding(ByVal sender As Object,
ByVal e As System.Windows.Controls.
DataGridRowEditEndingEventArgs) _
Handles BooksGrid.RowEditEnding
isEditing = False
End Sub
End Class

Now right-click the BookStoreTestPage.Aspx file in Solution Explorer and set it as the start page. Our application is now ready to be started. One of the biggest benefits of the Windows Azure SDK tools is that you can test your application locally before you deploy it to the cloud. This is possible because of the Windows Azure Simulation Environment that is a full-featured environment reproducing locally the cloud system.

Testing the Application Locally

When you run an Azure application locally for the first time, the environment needs to be initialized. Fortunately Visual Studio and the Windows Azure SDK will do the work for you. The first thing you notice is that the tools generate a new database on your machine; this is required for storing blobs, tables, and queues. This step also reserves local ports for reaching the previously mentioned contents locally. You can see this when you press F5. The Windows Azure Simulation Environment is started, and a dialog shows the progress of the database generation and IPs initialization, as represented in Figure 6.

Figure 6. Completion of the Simulation Environment initialization.

This also creates a local developer account that replicates on your local machine what you can activate on the online services. After you click OK, you can see the application correctly running in your web browser. Figure 7 demonstrates this.

Figure 7. The application running locally.

You can now try to add or delete other books and finally save changes. So we reached our objective locally. The next step should be deploying the application to the cloud, but doing making this, here’s some brief information about the Simulation Environment tools. The Simulation Environment is essentially composed of two main tools: the Development Storage, which is used for locally storing blobs, tables, and queues, and the Development Fabric that is useful for monitoring running services. The Simulation Environment provides a tray bar icon that you can right-click to access both tools. Figure 8 displays how the Development Fabric gives information about the running application.

Figure 8. The Development Fabric shows services information.

It is worth mentioning that the Development Fabric can show information about multiple running Azure services. Figure 9 shows instead the Development Storage UI. Notice that here you can just enable or disable endpoints for blobs, tables, and queues, but the suggestion is to leave unchanged the default settings.

Figure 9. The Development Storage user interface.

Because the application runs correctly, we can now deploy it to the cloud environment of Windows Azure.


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