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LANGUAGES: VB.NET | C#

ASP.NET VERSIONS: 2.x

Add Flash ... and Flare!

Grab Attention with this Free Custom Flasher Control

By Steve C. Orr

Flash animation is a great way to grab people’s attention among the endless sea of look-alike Web pages on the Internet. It can present useful information, as well as provide functional interactivity. Embedding Flash animation within a Web page used to be simple. However, changing standards such as XHTML and ActiveX Activation have introduced significant complications. In this article, you’ll learn all you need to know to play and embed Flash animations within ASP.NET Web pages. Indeed, the custom Flasher control detailed in this article makes Flash animation easy again.

Standards Challenges

Adobe’s Web site recommends the HTML syntax shown in Figure 1 to instantiate their Flash player and display a Flash animation. The syntax is not pretty, but it works — sort of. It certainly used to work well, but these days it has issues. For one thing, it violates the HTML standard in several different ways. Browsers tend to be forgiving, so for now it still mostly works. However, every good Web developer should strive for standards-compliant code. One of the main reasons it’s non-compliant is because the Embed tag is contained within the Object tag, which is not allowed. However, it works anyway, but only because Internet Explorer (IE) uses the Object tag and ignores the internal Embed tag, and Mozilla-based browsers do the opposite.

Figure 1. Adobe’s web site recommends this non-standard HTML to play Flash animations in a web page.

The sad fact is that there is no single HTML or XHTML-compliant syntax that will allow a Flash animation to be played across all browsers. Therefore, Web developers are pretty much forced to output one syntax for IE users and another syntax for other browser types. That is one messy detail that’s encapsulated by the custom Flasher control included with this article, so you won’t need to worry about it (see end of article for download details). Essentially, the Flasher control outputs HTML syntax similar to that shown in Figure 2 for all browsers except IE.

Figure 2. This HTML snippet will play a Flash file in all major browsers except Internet Explorer.

Conversely, the HTML in Figure 3 shows the syntax that works for IE. If that HTML is pasted into a Web page and references a valid Flash animation it will play just fine. However, an annoying message will appear to the user at run time.

Figure 3. This HTML snippet will play a Flash file in Internet Explorer — but ActiveX Activation will be required by the user upon every page load.

ActiveX Activation

The HTML in Figure 3 worked perfectly in 2005 — ah, the good old days. It turns out that a company named Eolas Technologies apparently has a patent on it. Microsoft’s stunning loss of the related lawsuit has had major repercussions for Web developers worldwide. Microsoft was forced to deploy patches for IE that now require the user to click (or press the spacebar) to activate any embedded software, such as ActiveX controls. Now users are presented with an annoying activation message for every Web site that still uses the old syntax (see Figure 4). It should be noted that the same issue also exists when trying to embed .NET Windows forms controls.

 
Figure 4. ActiveX Activation is a burden all Web developers must now deal with so their users don’t have to be annoyed by messages such as this.

To circumvent this problem, the only supported solutions (at the time of this writing) involve instantiating embedded ActiveX controls from an external JavaScript file (see this article for more information).

In short, if a Web developer wants standards-compliant code that plays Flash files in all browsers without requiring users to activate embedded ActiveX controls, there are quite a few hoops to jump through. All these issues have been addressed and resolved to drag-and-drop simplicity with the custom Flasher control described here.

Flasher!

To use the cross-browser compatible Flasher control, download the sample code and add the included Flasher.DLL to your Visual Studio 2005 toolbox. Then drag it onto any WebForm and set its FlashFile property to any valid SWF file. That’s it! Run the project and the Flash animation will play in all browsers without any of the headaches mentioned previously. Of course, you can customize it with various properties, such as those shown in Figure 5.

Unique Flasher Properties	Description
FlashFile	(Required) The URL to a Flash (.swf) file.
ns="urn:schemas-microsoft-com:office:smarttags" prefix="st1" ?>Loop	(Boolean) True will loop the animation infinitely; False will stop the animation at its end.
Menu	(Boolean) True to display an extended context (right-click) menu.
PlayImmediately	(Boolean) True to play the animation instantly upon page load.
Quality	(Enum) Allows different playback qualities for display devices of varying capabilities.  (AutoHigh is default)

Figure 5. The Flasher control provides several useful properties that allow versatile configuration.

The ASPX declaration looks like this:

<cc1:Flasher ID="Flasher1" runat="server"

FlashFile="~/anim.swf" BackColor="red"

Width="550" Height="400" Loop="false" />

If desired, JavaScript can be added to the page to let the user or page developer control the animation via client-side code. The following ASPX page code provides links to let the user start and stop the playback of the Flash animation:

So How Does It Work?

Flasher inherits from the System.Web.UI.Control class and extends it with custom rendering functionality and the properties shown in Figure 5. The overridden Render method is shown here:

At design time the Render method displays only a placeholder, as directed by the first line of code. The rest of the code simply branches to one run-time rendering routine for Internet Explorer users (RenderForIE) and another rendering routine for all other Web browsers (RenderForAlt).

The utilitarian RenderForAlt method shown in Figure 6 essentially uses a StringBuilder object to concatenate a string virtually identical to Figure 2 and renders it to the browser.

Figure 6. The RenderForAlt method takes care of the rendering tasks for all browsers except Internet Explorer.

This code is simpler than the IE rendering method because other browsers are not currently subjected to the burden of activation (and the extra code required to deal with it effectively).

Figure 7. The Flasher control’s Internet Explorer rendering method outputs only a single line of JavaScript, which calls the CreateIEFlash JavaScript function (shown in Figure 8).

ASP.NET 2.0 Embedded Web Resources

The RenderForIE method listed in Figure 7 essentially concatenates together this JavaScript, which is output directly into the page:

CreateIEFlash('Flasher', 'anim.swf',

  550,400,'#FFFFFF', true, true, 'high');

This code calls the custom JavaScript function (named CreateIEFlash) shown in Figure 8. The CreateIEFlash function essentially uses the document.write method to dynamically build and output HTML like that shown in Figure 3. To avoid ActiveX Activation, this function must be located in an external JavaScript file. Therefore, a reference to the external JavaScript file must be added to the page, such as this:

<script language="javascript" src="Flasher.js"></script>

Now, a person could try to remember to add this line to every page that uses the Flasher control, and a person could try to remember to deploy that JavaScript file to the proper location in every project that uses the Flasher control. However, it’s far more professional for the control to take care of these details itself.

Figure 8. This external JavaScript function dynamically outputs HTML similar to Figure 3. This technique avoids ActiveX Activation hassles.

Therefore, the JavaScript file has been compiled into the control as an embedded resource. To embed a file inside an assembly, simply drag the file into the project inside Solution Explorer, then set its Build Action property to Embedded Resource. To access this resource dynamically from the Web (as is about to be done), the file must also be declared. In this case, that’s done at the top of the class file (before the class declaration) with this design-time attribute:

<Assembly: _

System.Web.UI.WebResource("ControlFreak.flasher.js", _

"text/javascript")>

The new WebResource method available in ASP.NET 2.0 makes it possible for controls to manage their own resources to make deployment and maintenance easier. Its parameter accepts only the control’s namespace (ControlFreak), followed by a dot and then the filename with extension (flasher.js). The code in Figure 9 shows how the embedded JavaScript file is referenced dynamically at run time.

Figure 9. ASP.NET 2.0 includes the capability for Web controls to manage their own resources, which can greatly simplify deployment and maintenance.

Using this technique, the control’s JavaScript file doesn’t need to be located in the Web application’s directory structure at all; therefore, you can’t forget to put it there or accidentally put it in the wrong place. Instead, it’s automatically retrieved from the control at run time. The RegisterClientScriptResource function makes this happen by building a URL that references the embedded resource through an automatically managed HTTP Handler. The resulting HTML script tag looks like this:

<script src="/FlasherTest/WebResource.axd?d=t0e7oX8lfjsk…" type="text/javascript"></script>

Fun with Hexadecimals

Adobe’s Flash control requires its background color be set via RGB Hexadecimal values only. Color names are not supported. Therefore, I patched together a utility function to translate the Flasher control’s BackgroundColor property to just such a Hexadecimal value. This function is shown in Figure 10. You may have noticed it being called from the RenderForIE and RenderForAlt methods.

Figure 10. The Color2Hex function converts a color object into an RGB Hexadecimal value because that’s what Adobe’s Flash player requires.

This function extracts the Red, Green, and Blue (RGB) values from the Color object, then converts them in turn to hexadecimal values. Then the final line recombines them into a familiar string color value, such as this:

#FF0099

Wrap Up

Using the ASP.NET 2.0 WebResources techniques (shown here) and the GetWebResources method (not shown here), you can easily embed scripts, images, icons, strings, and other items on which a Web control might depend. Web controls can now control their own dependencies, thereby easing deployment and maintenance chores (see Figure 11).

 
Figure 11. The Flasher control plays Flash animations consistently across all major browsers so you don’t have to worry about development annoyances, such as ActiveX Activation or varying browser support.

The Flasher control makes playing Flash animations easy again. Now you can generate standards-compliant output that works in all browsers, and avoid user annoyances such as ActiveX Activation.

If you like this control then perhaps you'll also find my QuickTime player or Streaming Media controls useful as well.

The source code for the Flasher control is available for download here.

The original version of this article was published in the September 2006 issue of ASP.NET Pro Magazine.