Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Digging into the dependency property system

From: Silverlight 5 Essential Training

Video: Digging into the dependency property system

When you investigate a visual element like the button or list box, you see a lot of properties. You might be surprised to learn that most of these properties in Silverlight elements rely on specially UI system known as the Dependency Property System. This system was first conceived and created by the WPF team. This new system enhances the underlying .NET framework and permits elements to plug into useful services like Animation, data binding or styles. It is also important for Silverlight to be conservative with critical resources like memory. To provide these services, Silverlight relies on the Dependency System.

Digging into the dependency property system

When you investigate a visual element like the button or list box, you see a lot of properties. You might be surprised to learn that most of these properties in Silverlight elements rely on specially UI system known as the Dependency Property System. This system was first conceived and created by the WPF team. This new system enhances the underlying .NET framework and permits elements to plug into useful services like Animation, data binding or styles. It is also important for Silverlight to be conservative with critical resources like memory. To provide these services, Silverlight relies on the Dependency System.

There are two major parts of the Dependency system. In this movie, I will discuss the Dependency property. There is another movie in this chapter that covers Attached Properties. A core piece of the Dependency System is something called the Dependency Property. When you create a user control, you can choose whether to expose .NET properties or Dependency Properties. The correct approach is to do both. First, create a Dependency Property, so that your property can partake in Silverlight services like data binding. Also create a .NET property so that you will find it easy to set and read property values in code.

I'll show you how to write custom dependency properties in the next movie. As I said earlier, most of the properties on an element are dependency properties. The Buttons FontSize property is a good example. You can set the font size directly in code or a XAML, or the value of the font size could be set by one of the Silverlight services. Let me go to Visual Studio and show you how to set a property in code. I'm inside the DiggingIntoDependencyProperties project. And I'm going to go to this file called SettingDPInCode. Then I'm going to press F7 to switch to the code window.

These first two lines of code show how use the normal .NET properties. This is a .NET property called FontSize. I'm assigning a value of 40 to this FontSize. On line 26, I'm reading the value of the FontSize and assigning it to a variable. These are also exposed as Dependency properties, so I can go in code and say SetValue and GetValue. Now this syntax in SetValue, after I've pass the value which is the name of the property that I want to change and then the value that I want to assign to that property.

And the second line calling GetValue again passing in the property that I want to read the value from and then I need to do a cast because the data comes back typed as object. In my case I want to cast it to a double. As I mentioned earlier, one of the most notable features of Dependency Properties are that many different Silverlight services might be attempting to set the Dependency Property value. Silverlight takes a look, prioritizes each service and the highest priority service wins. I've listed on this page the priority resolution.

At the bottom, is the lowest priority and at the top is the highest priority. So let's take an example. I've set the font size in local value. That means I have assigned it in my XAML or in my code behind. I have set the font size to 40, but I have an active animation running. That's changing the font size from 20 to 80 and then back to 20 again. So, if I query the button and say what is your current font size? The Dependency System is going to look at the animation, sees that it has a higher priority value than the local, sees what the current animated value is and return that value to me.

In this example I'm going to work with all the controls that are in this folder, the Controls folder and I'm going to load those into this control called OrderOfPrecedence2. Let me show you a quick example of what this looks like when it's running. I'll press F5. When I click on these buttons, up at the top of the screen, it loads one of my user controls in. The first one shows with the Default Value is for the Fill value for this rectangle. And the second example shows setting it locally in XAML, and the third one shows setting it in code and so on.

The last one shows running in Animation. So it starts out at blue which is a relatively high priority setting and then the animation takes precedence over that. Returning to Visual Studio and opening this one here DefaultValue.xaml. This is my rectangle. Notice that nowhere in my XAML am I setting the Fill value. That means that the Dependency Systems are going to return the default. In the next example, I will look at setting it locally.

Local means setting it in XAML or setting it in code. In this case, I've specified in my Rectangle, a Fill value of LightBlue. That takes precedence over the default value. The third example sets it in code. So I start off by setting it locally, again to a LightBlue color. Then in my code behind page, press F7 to get there, when I click on this button I create a SolidColorBrush and assign that to the Fill.

That is also local, but it takes precedent over the one assigned in the XAML. If I ever want to remove the locally assigned value, I have to use the ClearValue function. Setting it to null does not accomplish what I want. There is a special function called ClearValue and you basically tell the dependency system, look up the default value and reassign that. Next I will look at setting it by style that's one of the higher priority items. Now in this example I have a Rectangle with no Fill value, but I've specified the Style attribute.

And I have told to use a markup extension to go look up a style that I have defined elsewhere, which you can see right up here is called the flamingoStyle and it's setting the Fill value to Pink. So styles take precedent over default. Another example with Styles shows that I have a style set here using that same flamingoStyle but I also have set it locally. If you look up the precedent order, styles are lower priority than local values, which is why the rectangle is orange.

If you have access to the exercise files, I encourage you to spend some time going through the examples yourself, so you can get more comfortable with the priority levels available within Dependency properties.

Show transcript

This video is part of

Image for Silverlight 5 Essential Training
Silverlight 5 Essential Training

106 video lessons · 5381 viewers

Walt Ritscher
Author

 
Expand all | Collapse all
  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

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ.

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Join now "Already a member? Log in

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Silverlight 5 Essential Training.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferencesfrom the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Are you sure you want to delete this note?

No

Your file was successfully uploaded.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.