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Silverlight 5 Essential Training

Handling global errors in a Silverlight application


From:

Silverlight 5 Essential Training

with Walt Ritscher

Video: Handling global errors in a Silverlight application

No matter how well you protect your code with exception handlers, errors can slip through your defenses. If you don't construct your own global handler, your application will use the Silverlight defaults. In this movie, I will show you how those defaults are configured, and how to implement your own error screens. For this demonstration, I will use Visual Studio and load a project called GlobalErrors. Let me show you the default UI before I introduce any exceptions. Press F5 to run the application and click on this Load vacation pictures, which loads a picture into the image control. My application is working as expected.
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  1. 1m 41s
    1. Welcome
      53s
    2. Using the exercise files
      48s
  2. 35m 0s
    1. Overview of Silverlight
      3m 29s
    2. Setting up a developer computer
      2m 46s
    3. Installing the Silverlight Toolkit
      2m 21s
    4. Exploring the toolkit samples
      2m 35s
    5. Using Visual Studio 2010 to create a Silverlight project
      5m 10s
    6. Using Expression Blend to create a Silverlight project
      3m 13s
    7. Getting to know the Visual Studio interface
      8m 15s
    8. Working in the Expression Blend interface
      7m 11s
  3. 29m 46s
    1. Understanding the Visual Studio project structure
      3m 38s
    2. Creating a Silverlight page
      3m 17s
    3. Compiling your first application
      5m 0s
    4. Using other assemblies in an application
      5m 45s
    5. Deploying a Silverlight application
      3m 43s
    6. Understanding the startup process for an application
      3m 13s
    7. Understanding how users get Silverlight on their computers
      5m 10s
  4. 16m 59s
    1. Exploring the relationship between XAML and .NET
      3m 57s
    2. Using C#
      7m 16s
    3. Exploring the code-behind file
      5m 46s
  5. 43m 22s
    1. Working with XAML elements and Property attributes
      4m 56s
    2. Investigating XAML namespaces
      7m 31s
    3. Converting XAML properties with TypeConverters
      5m 1s
    4. Working with Property elements
      4m 24s
    5. Assigning runtime data with XAML markup extensions
      4m 21s
    6. Digging into the dependency property system
      6m 12s
    7. Creating a custom dependency property
      4m 42s
    8. Understanding attached properties
      6m 15s
  6. 9m 35s
    1. Debugging your code
      5m 17s
    2. Special Silverlight debugging techniques
      4m 18s
  7. 36m 0s
    1. Understanding layout
      4m 55s
    2. Using DockPanel and WrapPanel
      4m 2s
    3. Exploring sophisticated layouts with the Grid
      6m 40s
    4. Absolute positioning with the Canvas panel
      5m 20s
    5. Scrolling content with the ScrollViewer
      3m 28s
    6. Adjusting content alignment, margins, and sizing
      5m 6s
    7. Using the TabControl
      2m 17s
    8. Manipulating elements with transforms
      4m 12s
  8. 20m 32s
    1. Painting the user interface (UI) with SolidColorBrush
      6m 7s
    2. Getting colorful with gradient brushes
      3m 15s
    3. Decorating elements with ImageBrush
      4m 56s
    4. Creating effects with VideoBrush
      6m 14s
  9. 25m 42s
    1. Understanding routed events
      3m 12s
    2. Wiring up event handlers in Silverlight
      6m 4s
    3. Understanding event bubbling
      4m 39s
    4. Exploring mouse events
      7m 43s
    5. Exploring keyboard events
      4m 4s
  10. 32m 31s
    1. Displaying text on the screen
      3m 24s
    2. Gathering text input from the user
      5m 30s
    3. Showing complex text with RichTextBox
      6m 7s
    4. Understanding text overflow and text linking
      3m 14s
    5. Searching content with the AutoComplete type-ahead control
      6m 45s
    6. Using and embedding Silverlight fonts
      7m 31s
  11. 26m 47s
    1. Understanding content controls
      5m 7s
    2. Understanding button controls
      6m 16s
    3. Using the BusyIndicator
      4m 40s
    4. Showing tooltips
      4m 34s
    5. Changing content size with ViewBox
      1m 39s
    6. Exploring more controls
      4m 31s
  12. 55m 36s
    1. Connecting elements with binding
      9m 54s
    2. Using business data in a binding
      9m 21s
    3. Listing data with ItemsControls
      6m 39s
    4. Digging into the DataGrid
      8m 28s
    5. Using the DataForm
      3m 49s
    6. Storing data on the client
      7m 10s
    7. Debugging XAML bindings
      5m 41s
    8. Charting data
      4m 34s
  13. 24m 36s
    1. Creating an Out-of-Browser (OOB) application
      6m 16s
    2. Controlling aspects of an OOB application
      2m 49s
    3. Alerting the user with notification windows
      7m 13s
    4. Hosting HTML content in Silverlight applications
      8m 18s
  14. 30m 2s
    1. Exploring Silverlight trust levels
      3m 51s
    2. Creating an elevated trust application
      5m 57s
    3. Reaping the benefits of XAP signing
      6m 5s
    4. Making cross-domain calls
      5m 1s
    5. Getting started with COM Interop using the Speech API
      4m 21s
    6. Using COM Interop to interact with Microsoft Office
      4m 47s
  15. 16m 33s
    1. Showing child windows
      3m 48s
    2. Using a child window as a dialog window
      5m 7s
    3. Creating native windows
      2m 53s
    4. Maximizing a window with full screen mode
      4m 45s
  16. 13m 20s
    1. Dynamically loading UI content with user controls
      4m 46s
    2. Using the Navigation Framework
      8m 34s
  17. 9m 28s
    1. Using resource files
      3m 53s
    2. Using images in an application
      5m 35s
  18. 16m 32s
    1. Playing audio
      4m 27s
    2. Playing sound effects
      5m 4s
    3. Viewing video content with MediaElement
      4m 58s
    4. Changing video playback speed with TrickPlay
      2m 3s
  19. 14m 40s
    1. Capturing video with a web camera
      4m 16s
    2. Working with a microphone
      3m 47s
    3. Creating print output
      6m 37s
  20. 22m 35s
    1. Understanding Silverlight animations
      4m 35s
    2. Creating animations
      7m 52s
    3. Controlling animations
      4m 18s
    4. Simulating physics with animation easings
      5m 50s
  21. 27m 47s
    1. Placing XAML resources within a FrameworkElement
      6m 47s
    2. Centralizing settings in styles
      4m 8s
    3. Creating an alternate control UI with ControlTemplates
      6m 29s
    4. Dressing up your data with DataTemplates
      4m 33s
    5. Explaining the VisualStateManager: a simple way to manage control states
      5m 50s
  22. 10m 55s
    1. Handling global errors in a Silverlight application
      5m 46s
    2. Showing an application loading screen
      5m 9s
  23. 10m 48s
    1. Integrating with XNA
      7m 40s
    2. Exploring data analysis with PivotViewer
      3m 8s
  24. 1m 6s
    1. Goodbye
      1m 6s

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Silverlight 5 Essential Training
8h 51m Beginner Mar 27, 2012

Viewers: in countries Watching now:

Microsoft Silverlight 5 is a rich application framework for creating high-performance, cross-platform desktop and mobile applications. In this course, author Walt Ritscher demonstrates how to build a variety of applications in Silverlight, with particular focus on building compelling business applications and delivering premium video and audio content. Developers will work with the C# programming language and Visual Studio Professional, as well as Expression Blend, a tool that simplifies creation of the interactive user interfaces expected in modern-day applications.

Topics include:
  • Installing the toolkit and setting up the development environment
  • Using Expression Blend vs. Visual Studio 2010
  • Creating a Silverlight page
  • Compiling an application
  • Exploring the relationship between XAML and .NET
  • Using C#
  • Working with XAML
  • Digging into the Dependency Property System
  • Deploying and debugging code
  • Creating sophisticated layouts with panel elements
  • Managing Visual State with Visual State Manager
  • Transforming the user interface (UI) with templates
  • Understanding the event model
  • Working with text
  • Using business data in a binding
  • Creating an out-of-browser (OOB) application
  • Exploring trust levels
  • Playing audio and video
  • Handling errors
  • Exploring animations
  • Working with application windows
  • Integration with XNA
Subject:
Developer
Software:
Silverlight Visual Studio
Author:
Walt Ritscher

Handling global errors in a Silverlight application

No matter how well you protect your code with exception handlers, errors can slip through your defenses. If you don't construct your own global handler, your application will use the Silverlight defaults. In this movie, I will show you how those defaults are configured, and how to implement your own error screens. For this demonstration, I will use Visual Studio and load a project called GlobalErrors. Let me show you the default UI before I introduce any exceptions. Press F5 to run the application and click on this Load vacation pictures, which loads a picture into the image control. My application is working as expected.

Let me introduce a bug into my code. I will go to my MainPage.xaml.cs file, and I am going to change the name of this file from a C to a K. So we'll say kabin.jpg. This should cause an exception when it attempts to load the stream. I am ready to test, but before I do, let's talk about the Debug menu. I have two choices for starting my app from Visual Studio: Start Debugging and Start Without Debugging. Now you may recall that when you choose Start Debugging, Visual Studio starts the Browser and then attaches a debugger to the browser.

So I can debug my code. That's important keep that in mind. Press Start Debugging. I will click in my button again. Visual Studio detects that I have an expression and gives me an opportunity to debug the exception. It does that by putting a yellow marker here on this line, stopping my code from running, and pulling up this little exception dialog. There is lots of information inside this dialog. If you click View Details, you can see some of them. For instance, I can see that it was a NullReferenceException. I can see some Data. I can click on the InnerException and see if there is any nested exceptions and Message and the StackTrace as well.

My other choice was to run this without attaching the Debugger, so let me show you what happens when I do that. Start Without Debugging. I clicked on the button and now I am getting this dialog. Visual Studio sees that I have an exception in my JavaScript code and gives me another opportunity to debug this application. How does that happen? Let me show you. If I go to Tools > Options and then go to Debugging > Just-In-Time, this checkbox here it gives me an opportunity to, just in time, debug my JavaScript.

Where is that JavaScript exception coming from? I will show you. I am going to go to my Application and choose Show All files. Then I am going to drill down into my Bin folder and my debug folder and find the test page that's generated by Visual Studio. This is the same as the HTML page you would have if you had a companion ASP.network site. When I double-click on the HTML page and look in this area where the Silverlight plug-in is loaded, I can see that on line 63 the plug-in is registering a JavaScript function called onSilverlightError.

So if an exception comes out of this Silverlight application is not handled by Silverlight, it gets to the plug-in and then this JavaScript code runs here. As you cab see, the bulk of this code is setting up error messages, and then at the bottom it's throwing that error message. Let's look at that error message inside the browser. Go to Tools > Options, turn off the script just in time debugging, start my application without a debugger attached. Then I will turn on the Developer tool inside Internet Explorer by pressing F12, and then clicked on Console.

Now I can see the error in this bottom window. There it is. It was an Unhandled Error in Silverlight Application, the error code, and some other information about the error. Currently, I have no exception handling at the Global level inside my app. Let's change that. I will go to App.xaml.cs. Here inside my constructor, I have two sections where I could set up an exception handler. This is the standard Boilerplate code that Microsoft produces, and this is the custom code that I wrote.

Uncomment this line of code, and then I go look at my custom handler. Here it is. The first thing that I do in Customer Handler is I tell Silverlight to not let the error get to the Silverlight plug-in. I do that by saying e.Handled=True, e being this argument here, ApplicationUnhandledExceptionEventArgs. Next, I report my error to my own UI. What I am doing here is going to my main page, which is called the RootVisual. The RootVisual is the startup control inside your Silverlight application. Here you can see I am instantiating an instance of this class MainPage.xaml.

So in my custom exception handler, I am getting the RootVisual, I am calling a Custom method that I wrote call ShowErrorMessage, and I am passing in the exception. Now if I come over to my custom page and look at the code behind, you can see that the custom function that I wrote, ShowErrorMessage. Now what I am doing in here? I am creating my own UI, which is a child window called ErrorDialog, and then I am passing some information into my child window, and then I am showing that window. So that means of course if it created this ErrorDialog, here I can create my own beautiful UI for my exceptions and then on this TextBlock, I am going to load that in my code behind through this property. Time to see the application in action.

I will choose to Start Without Debugging, click on the button, and there is my custom error message. From my last demo, I thought we would look briefly at Microsoft's boilerplate code. Let's go over to App.xaml.cs. We'll scroll down to this section, which is a region that I put in my code. What Microsoft does in their boilerplate code is, inside this method, they check to see if there's a debugger attached, set the e.Handled=True and then do an asynchronous BeginInvoke call to a function they wrote called ReportErrorToDOM.

That function, which is down here, creates a new error message, and finally, it goes to the HTML page and throws a new error. The default handlers in Silverlight are a good start, but you can do better. In the next movie, you will see how to create custom loading screens in your application.

Find answers to the most frequently asked questions about Silverlight 5 Essential Training.


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Q: I'm trying to access a Silverlight 3D application template, [cid:image001.png@01CD0E7D.3E07ECA0]. I have already installed the Silverlight 5 SDK and my Visual Studio 2010 is professional. Could you please help me?
A: You must install XNA Studio in order to use the new Silverlight 3D templates. Otherwise the new templates will not show up. Download it at http://www.microsoft.com/download/en/details.aspx?id=23714.

For other Silverlight downloads (the toolkit, developer runtime, etc.), see http://www.silverlight.net/downloads.
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