Exam objectives in this chapter:

• Configure event handling.
• Configure commands.
• Configure application settings.

Quick Check

• What are the three kinds of routed events in WPF and how do they differ?

Quick Check Answer

• Routed events in WPF come in three different types: direct, tunneling, and bubbling. A direct event can be raised only by the element in which it originated. A bubbling event is raised first by the element in which it originates and then is raised by each successive container in the visual tree. A tunneling event is raised first by the topmost container in the visual tree and then down through each successive container until it is finally raised by the element in which it originated. Tunneling and bubbling events allow elements of the user interface to respond to events raised by their contained elements.

Selected Application-Level Events

Event	Description
Activated	Occurs when you switch from another application to your program. It also is raised the first time you show a window.
Deactivated	Occurs when you switch to another program.
DispatcherUnhandledException	Raised when an unhandled exception occurs in your application. You can handle an unhandled exception in the event handler for this event by setting the DispatcherUnhandledExceptionEventArgs.Handled property to True.
Exit	Occurs when the application is shut down for any reason.
SessionEnding	Occurs when the Windows session is ending, such as when the user shuts down the computer or logs off.
Startup	Occurs as the application is started.

Application events are standard .NET events (rather than routed events), and you can create handlers for these events in the standard .NET way.

Lesson Summary

• WPF applications introduce a new kind of event called routed events. Routed events are raised by WPF controls.
• There are three kinds of routed events: direct, bubbling, and tunneling. Direct events are raised only by the control in which they originate. Bubbling and14 tunneling events are raised by the control in which they originate and all controls that are higher in the visual tree.
• A tunneling event is raised first by the top-level control in the visual tree and tunnels down through the tree until it is finally raised by the control in which it originates. A bubbling event is raised first by the control in which the event originates and then bubbles up through the visual tree until it is finally raised by the top-level control in the visual tree.
• You can attach events that exist in contained controls to controls that are higher in the visual tree.
• The EventManager class exposes methods that allow you to manage events in your application. You can register a new routed event by using the EventManager .RegisterRoutedEvent class. You can create a class-level event handler by using EventManager.RegisterClassHandler.
• The Application object raises several events that can be handled to execute code at various points in the application’s lifetime. You can handle application-level events in the code for the Application object.

Lesson Review

You can use the following questions to test your knowledge of the information in Lesson 1, “Configuring Events and Event Handling.” The questions are also available on the companion CD of this book if you prefer to review them in electronic form.

1. Suppose you have the following XAML code:

   <Window x:Class="WpfApplication1.Window1"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="Window1" Height="300" Width="300"
      ButtonBase.Click="Window_Click">
      <Grid ButtonBase.Click="Grid_Click">
         <StackPanel Margin="47,54,31,108" Name="stackPanel1"
            ButtonBase.Click="stackPanel1_Click">
            <Button Height="23" Name="button1" Width="75">Button</Button>
         </StackPanel>
      </Grid>
   </Window>

   Which method will be executed first when button1 is clicked?

   1. Button1_Click
   2. stackPanel1_Click
   3. Grid_Click
   4. Window_Click
2. Suppose you have the following XAML code:

   <Window x:Class="WpfApplication1.Window1"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     Title="Window1" Height="300" Width="300" MouseDown="Window_MouseDown">
     <Grid PreviewMouseDown="Grid_PreviewMouseDown">
        <StackPanel Margin="47,54,31,108" Name="stackPanel1"
           PreviewMouseDown="stackPanel1_PreviewMouseDown">
           <Button Click="button1_Click" Height="23" Name="button1"
               Width="75">Button</Button>
        </StackPanel>
     </Grid>
   </Window>

   Which method will be executed first when button1 is clicked?

   1. Window_MouseDown
   2. Grid_PreviewMouseDown
   3. stackPanel1_PreviewMouseDown
   4. button1_Click
3. You are writing an application that consists of a single WPF window. You have code that you want to execute when the window first appears and every time the window is activated. What application event or events should you handle to accomplish this goal?
   1. Activated
   2. Startup
   3. Activated and Startup
   4. Deactivated and Startup

Lesson 2: Configuring Commands

• Explain the different parts of a command
• Associate a command with a UI element
• Add a gesture to a command
• Execute a command
• Associate a command with a command handler
• Disable a command
• Create a custom command

Commands allow you to use a centralized architecture for tasks. You can associate any number of UI controls or input gestures to a command and bind that command to a handler that is executed when controls are activated or gestures are performed. Commands also keep track of whether or not they are available. If a command is disabled, UI elements associated with that command are disabled, too.

Command architecture consists of four principal parts. There is the Command object itself, which represents the task. Then there are command sources. A command source is a control or gesture that triggers the command when invoked. The command handler is a method that is executed when the command is invoked, and CommandBinding is an object that is used by the .NET Framework to track what commands are associated with which sources and handlers.

The .NET Framework provides several predefined commands that are available for use by developers. These built-in commands are static objects that are properties of five static classes, which are the following:

• ApplicationCommands
• ComponentCommands
• EditingCommands
• MediaCommands
• NavigationCommands

Each of these classes exposes a variety of static command objects that you can use in your applications. While some of these commands have default input bindings (for example, the ApplicationCommands.Open command has a default binding to the key combination Ctrl+O), none of these commands has any inherent functionality—you must create bindings and handlers for these commands to use them in your application.

Command Bubbling

Note that all controls have their own CommandBindings collection in addition to the window’s CommandBindings collection. This is because commands, like routed events, bubble up through the visual tree when they are invoked. Commands look for a binding first in the CommandBindings collection of the control in which they originate, and21 then in the CommandBindings collections of controls higher on the visual tree. Like a routedEvent, you can stop further processing of the command by setting the Handled property of the ExecutedRoutedEventArgs parameter to True

Lesson Summary

• Commands provide a central architecture for managing high-level tasks. The .NET Framework provides a library of built-in commands that map to common tasks that can be used in your applications.
• Commands can be invoked directly, by an input gesture such as a MouseGesture or a KeyGesture, or by activating a custom control. A single command can be associated with any number of gestures or controls.
• CommandBindings associate commands with command handlers. You can specify a method to handle the Executed event of a command and another method to handle the CanExecute event of a command.
• Methods handling the CanExecute event of a command should set the CanExecute property of the CanExecuteRoutedEventArgs to False when the command should be disabled.
• Commands can be bound by any number of CommandBindings. Commands exhibit bubbling behavior. When invoked, commands first look for a binding in28 the collection of the element that the command was invoked in, and then look in each higher element in the visual tree.
• You can create custom commands. When you have created a custom command, you must map the namespace in which it exists to a XAML namespace in your XAML view.

Lesson Review

You can use the following questions to test your knowledge of the information in Lesson 2, “Configuring Commands.” The questions are also available on the companion CD if you prefer to review them in electronic form.

1. Which of the following is required to bind a command to a command handler? (Choose all that apply.)
   1. Instantiate a new instance of CommandBinding
   2. Set the CommandBinding.Command property to a command
   3. Add one or more input gestures to your command
   4. Add a handler for the CommandBinding.Executed event
   5. Add a handler for the CommandBinding.CanExecute event
   6. Add CommandBinding to the CommandBindings collection of the Window or other control associated with the command
2. You are working with an application that exposes a command named Launch. This command is registered in the CommandBindings collection of a control called Window11 and requires a String parameter. Which of the following code snippets invokes the command from code correctly?29

   1. ' VB
      Launch.CanExecute = True
      Launch.Execute("Boom", Window11)
      
      // C#
      Launch.CanExecute = true;
      Launch.Execute("Boom", Window11);

   2. ' VB
      Launch.Execute("Boom")
      
      // C#
      Launch.Execute("Boom");

   3. ' VB
      Launch.Execute("Boom", Window11)
      
      // C#
      Launch.Execute("Boom", Window11);

   4. ' VB
      Window11.CanExecute(Launch, True)
      Launch.Execute("Boom", Window11)
      
      // C#
      Window11.CanExecute(Launch, true);
      Launch.Execute("Boom", Window11);

I was so excited to finally get started on my internship. I thought to myself, “Hey, you could treat this like any job and it should be pretty easy,” but as I thought about it more on my drive from Fort Worth to Dallas I started to really take in the possibilities that could stem from this new experience. I have only done one internship in the past and honestly it was a joke of an experience. Sad to say, I think I knew a lot more about the industry and how to do the work than the people who worked there. Today, I am fairly sure that is not the case and that makes me happy.

Well, not only was I was suppose to start my first shift at 1pm, I had arrived early. However, I could not enter the building because no one was around. I guess it was about lunch time and just sat in my Jeep for about 10-15 minutes or so. Until people started to show up. Still stood outside for about a couple of minutes until the receptionist, Rose Marie, finally noticed I was standing outside. Apparently the call button on the intercom was acting up and she never heard the multiple times I was pushing it. Since Anna (Cheng), The 33 TV’s Creative Department Web Developer and my supervisor contact for the internship, was still not back from lunch I stood around talking with Rose about various things, but the obvious topics were the current remodeling construction that was taking place and my first day as an intern.

I was once told that one of the ultimate and most important people you can ever network with is the secretary/receptionist of a company. The reason is that they are the center of a lot of information about the company and more importantly, they know everyone. Make the receptionist mad or be rude to them and they could make your life hell because a lot of people of whatever company value their input and impressions of the people who visit. I have even heard of interviews that ended early based on the interviewers inquiry from the receptionist about the interviewee.

Eventually, Anna arrived (about 5 minutes after 1pm), got me signed in and we were off to her office in the Creative Department to get started. Much like our interview, we went over a few things about the internship and some things I could expect along the way. We went over the website again, which apparently I had confused with the actual CWtv.com site with the33tv.com site (I knew something was not right about that when I was looking at the site), but the stations site was easy enough to understand where everything was. In addition, she went over the tools that I was going to be using during the development of site pages and content uploads.

One tool was their browser based proprietary Content Management System (CMS) called Assembler that is used throughout all the Tribune networks. Its has bit of a “cloud computing” feel to the whole idea of it, since one can view images and content from any television station or newspaper that is associated with the Tribune network…even Associated Press. The second tool is their proprietary front end system P2P, not Peer-to-Peer as the abbreviation is better known as, but more like Power-to-Producer or something like that, Anna and I had a laugh over that since it really does not give a producer any more power than usual, but the actual name of it really is not as important as what it does.

Overall, I kind of understand Assembler, but it is kind of confusing at the same time as there seems to be an excessive amount of steps to just simply upload content. At least, that is how it seems at this moment, a little overwhelming. The P2P tool is a little easier to understand as it is pretty straight forward. To build a page it is as simple to just duplicate a page that has been previously created with a layout you are looking for then input the “slugs” (paths to content created in Assembler – and apparently I just found out that WordPress uses slugs too) into the appropriate sections where you want the content to be viewed and being basically a drag-and-drop interface makes it actually easier to use. It is a little more in depth, but it is more steps taken to get to the final result rather than a discussion topic.

As Anna said, the best way to really get to know these tools is to jump right in and start using them to get the feel of where things are and how things work. I agreed and started on my first project to design a banner and page for the Six Flags Over Texas and The 33’s “Scream Test” contest on Saturday, October 10, 2009.

Anna is pretty laid back on how things are to get done. There is an objective and then whatever we need to do to get it done, we do it. She tells me that I have creative freedom to complete a task when building the banner for the event.

Now personally, I have a bad history with this phrase “creative freedom” because in my experiences (with my current job) when someone says that I almost always have to re-do something because the client did not like the look of it, even after we have spoken and I explained what I was going to do. So I approached this project with a grain of salt to complete. When I created the banner I had to use Photoshop CS2. I was taken aback to find out that it was only recently installed. Being a Photoshop junkie, it is a good thing that I know how to use the program pretty good, but I realized how spoiled I was using the newer versions when certain tools and layouts were missing from my repertoire of tools in the program. It was easy to adjust however and the overall result so far is found here –> Scream Test. After the contest is over, the team that worked it will decide on the finalist and then a winner. There was suppose to be streaming video of it, but they could not get that to work correctly. However, they are suppose to provide me with images to create a photo gallery next week. When I completed that, Anna said that she really liked it, which took some weight off of the whole “creative freedom” situation.

Anna then took me on a tour of the station and introduced me to a lot of people. I have few names written down on my notepad, but there were so many people that I really do not remember any of the top of my head or any at all. I use to work for Warner Brothers/Time Warner and at one point had actually been to this television station before when it was the WB quite some time back about 6-8 years ago I would guess, so the station itself was not new to me per say, but more that some of the layout had changed and really many of the people were different. In fact I caught myself about to refer to it as being the WB33 a few times, since that is what I knew it as. LOL! I will get use to the fact that it is now just “The 33″ soon, but it will take a bit of conditioning and I am sure working on the site will help fix that.

Day 2 – Thursday, October 8, 2009 – 8:30am to 1:30pm = 5 hrs, Total: 9hrs:

Traffic this morning sucked! On top of that, the rain did not help that at all. I took off at 6:30am and still arrived about five minutes late. Lucky for me, Anna was running late as well for a similar reason. Anyhow, my plan was to get their early enough that I could pick up breakfast from the Jack-in-the-Box down the street, but that did not happen. Well at least not right away. Anna let me step out really quick to go grab a bite to eat because I was starving and very grateful for the opportunity.

My second day was actually quite a bit easier and it seems that a lot of the things I learned in using Assembler and P2P actually stuck in my mind. There were however moments where I had to ask Anna what steps I needed to take to do something, but that is the learning process with something new. Cannot learn it all at once, but I do seem to be catching on quickly. I was suppose to continue creating stuff for the “Scream Test,” but the content I needed was not available as Anna had anticipated and the techs still could not get the streaming video to work correctly for it, so we moved on to other things.

In addition to the Community Calendar, I will also be in charge of creating Photo Galleries, and the “CWikies” (synonym for “quickies,” yeah I know, I thought it was cute too), the HTML newsletter that is sent out to about 24 thousand viewer subscribers that they will receive in their email. Awesome!

My first task was to update the Community Calendar by imputing the submitted events into Assembler by creating content into the existing “collection” for the community calendar section. After about the fourth or fifth one I was moving along pretty quickly and really started to get the hang of Assembler. In fact I was done so quickly that is when Anna told me about the CWickie newsletter and so I got started on that. About half-way through, Anna told me to go get some food cause by this point I was starving. When I returned I had informed her that I wanted to go over my “Learning Objectives” and after a couple of minutes we started on that. I think there is some pretty cool stuff to look forward to on there, especially the iPhone application stuff. I cannot wait to find out what that is about.

So after going over the learning objectives and eating, I began working on the newsletter graphics once again. It took me a little longer to complete because I am very thorough and anal about organization. By that I mean the file I was given as a template to work with to create the newsletter was so unorganized that there were layers in places that did not make sense to the design and come to find out that they were part of the old newsletter design. As well, almost nothing was labeled which is something that really gets on my nerves and why I would just sometimes rather start from scratch rather than try to work from someones previous work. Why do not people label things? Anyhow, after getting passed all that and organizing things I was able to really start creating the design elements to the newsletter. I had to keep requesting logos because none of them were immediately available for use.

While working on this, Anna told me that they needed a logo/graphic to use as a banner/poster at the “Scream Test” event at Six Flags and instead of having to create one, they were likely to use the logo and graphic that I had created for the banner. *smile* Pretty cool. I was told that they like my design styles and use of space and colors.

The time passed quickly today as 12:30pm was up before I knew it and people were leaving for lunch. I was not completely done with the newsletter elements by this time and a lot of the time I cannot stand leaving stuff unfinished when it is so close to being done. So I ended up staying an extra hour to complete the newsletter because I had the time to do so and to actually satisfy my need to accomplish something for the day. Then I wrote a note to Anna about the completed work and where she could find it on the computer and headed off for the day.

I think that this first week went really well. I realize that although I already understand and have learned a lot at The 33 as an intern, I have a lot more still to learn. I feel I am really getting the hang of Assembler, but let me see how I feel about that on Tuesday and how much I remember. Still need to work in P2P more, I am suppose to start on Photo Galleries next week also, so that will give me opportunity to work with this tool. Also looking ahead, I was hoping to be able to attend the “Scream Test” at Six Flags, but there is a lot on my plate and it does not look like I will get to make it. I am still quite excited about the things to come. Next week I will be changing my schedule up a bit and will be going in on Tuesday morning instead of Monday afternoon, in hopes that it will work better for my schedule since I have class all day after.

DOM, Document Object Model for XML that extended to be used in HTML. In XML and HTML Document consist hierarchy of nodes with different types of data. DOM allows unprecedented control over web pages. Nodes can be added, removed, replaced and modified easily.

DOM Core was the API developed to handle XML documents, DOM HTML extended DOM Core by adding HTML specific objects and methods. DOM is not JavaScript specific, it is implemented in numerous other languages as well, where as DOM for web implemented using ECMAScript, and makes up to large part of JavaScript.

Idea behind W3C developing DOM Level 1 (1998) was to map structure of a document. Aims of DOM Level 2 was much broader including support for events, range, traversal of document, and support for CSS. Level 1 also extended to support XML namespaces.

Following new modules were introduced in DOM Level 2

DOM Event

DOM Style

DOM Views

DOM Range and Traversal

DOM 3 further extend DOM to introduces methods to Load and Save documents in uniform way, and also methods to validate DOM

DOM, Document Object Model for XML that extended to be used in HTML. In XML and HTML Document consist hierarchy of nodes with different types of data. DOM allows unprecedented control over web pages. Nodes can be added, removed, replaced and modified easily.

DOM Core was the API developed to handle XML documents, DOM HTML extended DOM Core by adding HTML specific objects and methods. DOM is not JavaScript specific, it is implemented in numerous other languages as well, where as DOM for web implemented using ECMAScript, and makes up to large part of JavaScript.

Idea behind W3C developing DOM Level 1 (1998) was to map structure of a document. Aims of DOM Level 2 was much broader including support for events, range, traversal of document, and support for CSS. Level 1 also extended to support XML namespaces.

Following new modules were introduced in DOM Level 2

DOM Event

DOM Style

DOM Views

DOM Range and Traversal

DOM 3 further extend DOM to introduces methods to Load and Save documents in uniform way, and also methods to validate DOM