Mark J. Collins

Drag and Drop

The ability to select an element and drag it to another location is an excellent example of a natural user experience. I can still remember the early Apple computers where you could delete a file by dragging it onto a trash can icon. This action, and hundreds more like it, are a key component of user experiences found on desktop applications. Web applications, however, have lagged far behind in this arena. With the drag and drop (DnD) API in HTML5, you’ll find web applications rapidly catching up.

Scalable Vector Graphics

In this chapter, I’ll show you how to use Scalable Vector Graphics (SVG) in an HTML5 web application using Visual Studio, ASP.NET MVC, and SQL Server. There are a lot of really cool things that you can do with SVG. I’ve picked out a fun demonstration that can be easily applied to many business applications. But first, let me give you an introduction to what SVG is.

Audio and Video

In this chapter, I will demonstrate the new audio and video elements introduced with HTML5. The two elements are identical in terms of their attributes and the methods and events that they support. I will spend most of the chapter discussing and demonstrating the audio element but just keep this in the back of your mind that everything I’m showing you applies to video as well. There are some exercises at the end of the chapter that will apply these same techniques to the video element so you can see this for yourself.

Structural HTML Elements

I briefly introduced the basic HTML syntax in Chapter 1 and then explained the information inside the head element. There is no displayable content in the head element; the data there is intended for applications to use such as browsers, screen readers, or search engines. Now we turn our attention to the body element; this is where the content goes.

Mobile Web Applications

So far, we have only looked at desktop browsers, however, one of the really great aspects of HTML5 is how well it is supported on a wide variety of devices including mobile phone, tablets, and TVs. In fact, the number of HTML5 devices is expected to exceed 1 Billion by 2013 (see the article at www.strategyanalytics.com/default.aspx?mod=pressreleaseviewer&a0=5145). As of this writing, the Opera Mobile and Firefox Mobile platforms lead the pack with 369 and 325 points, respectively, as reported by Html5Test.com. When Blackberry 10 releases, it is expected to receive a whopping 447 points out of a possible 500.

Compensation, Confirmation, and Cancellation

When working with long-running workflows that can take hours or even days to complete, you often need to handle the scenario in which something goes wrong and the workflow cannot be completed. The activities that have already executed may need to be “undone” in some fashion. As part of the workflow design, you should plan for these situations. In this chapter, you’ll use the techniques provided by WF to incorporate the necessary cleanup activities into your workflow design.

Send and Receive

The primary activities used for communication are the Send and Receive activities (and their variations SendReply and ReceiveReply). These activities use the Windows Communication Foundation (WCF) to transmit and listen for messages. In this chapter, you’ll build a simple console application that uses workflow to communicate with another copy of the same application.

Building a Simple Workflow

Let’s start by building a simple workflow. Start Visual Studio (VS) 2010 and select the New Project link. Under the Installed Templates, navigate to Visual C#, Workflow and you should see that four templates have been provided. Select the Workflow Console Application, as shown in Figure 1-1. Enter the name as Chapter01 and select a suitable location for this solution. Open image in new window Figure 1-1. Creating a new workflow project

Extending the Built-In Activities

In this chapter, you’ll start with the project from Chapter 6 and refine the order pricing rules. In the process, I’ll demonstrate two techniques for extending the built-in activities: creating custom activities and using the InvokeMethod activity.

Communicating with the Host Application

In this chapter, you’ll build a solution similar to the one from Chapter 8, except that you’ll replace the console application with a Windows Presentation Foundation (WPF) application. In the projects you’ve built so far, the host simply invoked the workflow and displayed the results upon completion. With this project you’ll need a lot more communication between the workflow and the host application. Fortunately, WF 4.0 provides the features you’ll need to accomplish this.