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Posts from July 2008

Read a Silverlight book - with Silverlight! [SimpleSilverlightXpsViewer adaptation by Laurence Moroney]

At the bottom of the post on migrating SimpleSilverlightXpsViewer to Silverlight Beta 2, I hinted at "a cool, practical, relevant use of SimpleSilverlightXpsViewer that I'll be able to share sometime soon". "Soon" is now, and I'm happy to point readers at the "Read about Silverlight in XPS" post by Laurence Moroney in which he uses an adaptation of my viewer for showcasing the first three chapters of his new book, Introducing Microsoft Silverlight 2.

Here's what it looks like - just click the image to try it out for yourself:

Screen shot of the XPS Viewer adaptation

In addition to modifying the sample for his purposes, Laurence went further and integrated mouse wheel support: zooming in and out is as easy as spinning the wheel. I've got to agree that it's a very nice usability improvement!

Since releasing the XPS Viewer Sample, a few people have expressed interest in repurposing the code for something similar. Kudos to Laurence for doing a great job with this - and I love that it's being used to help spread the word about Silverlight! :)

Maintaining access to Silverlight 2's generic.xaml resources [SilverlightDefaultStyleBrowser updated for build 2.0.30523.8 and beyond!]

A few days ago the Silverlight team released a minor update to Beta 2, changing the version number from 2.0.30523.6 to 2.0.30523.8 in the process. The version number is part of Silverlight's install path and SilverlightDefaultStyleBrowser (background reading available here, here, and here) didn't know to look in the new location when automatically importing Styles. As such, when run on machines with the updated Silverlight bits, the list was missing Styles for the core controls like Button, ListBox, etc.. (As I discovered for myself a short while ago when I tried to use SilverlightDefaultStyleBrowser!)

I've just updated SilverlightDefaultStyleBrowser to look in all subdirectories of %ProgramFiles%\Microsoft Silverlight when starting up. Not only does this fix the current problem, but it should save me from having to do anything next time there's an update, as well! :)

The version number of SilverlightDefaultStyleBrowser always appears in the window's title and the latest release number is 1.0.3123.31689. (Note: I haven't updated the screen shot below which shows the introductory version number.) If installed via ClickOnce, the application should automatically prompt you to upgrade once it detects the update (which typically happens after running the app once or twice). If you're using the standalone EXE, you'll need to update manually.

SilverlightDefaultStyleBrowser Application

Click here or on the image above to install SilverlightDefaultStyleBrowser via ClickOnce with automatic updating.

Click here to download the standalone SilverlightDefaultStyleBrowser executable and source code in a ZIP file.


  • On most machines it seems that the upgrade to Silverlight version 2.0.30523.8 automatically uninstalled the bits for 2.0.30523.6. However, on some machines (like one of mine!), the uninstall of 2.0.30523.6 was skipped or incomplete. So it's possible that SilverlightDefaultStyleBrowser's new behavior of importing from all directories under %ProgramFiles%\Microsoft Silverlight will import Styles from more than one version of Silverlight. To help avoid confusion - and to support multiple side-by-side installations of Silverlight in the future - I've modified the ToolTip for the ListBox items to display the path of the assembly from which that Style came. So if you see multiple Button Styles in the list, just hover over each of them to see where they came from - then pick the one that matters to you!
  • I've tweaked the ListBox item ToolTip to pop up when the mouse is over any part of the item (instead of just the Style's name). This was a simple matter of adding HorizontalContentAlignment=Stretch to the ListBoxItems via the ListBox's ItemContainerStyle property.

I'm sorry for any trouble the recent Silverlight upgrade may have caused! The good news is that this particular problem shouldn't happen again. :) And if it does, you can always use the "Add Assembly" button to manually import Styles from any file(s) you want until I get around to fixing things.

Smaller is better! [A simple step to shrink the download size of Silverlight 2 applications]

When putting content on the web, it's important to get that content to the user as quickly as possible. In general, reducing the amount of data users need to download is a big step in the right direction. As such, the XAP packaging format used by Silverlight 2 wraps everything in a single, compressed archive file that's browser-friendly. At the moment, the compression for XAP files in Beta 2 is not as efficient as it could be, and XAP files tend to be a bit larger than necessary. Until this is addressed in a future release of the Silverlight tools, here is something that's almost as good. :)

XAP files are really just standard ZIP files with a different extension, so we can use ZIP-file tools to improve the XAP situation quite easily. I wrote a simple batch file named XapReZip.cmd (contents below) that can be added to a Visual Studio 2008 Silverlight project to automatically re-compress the project's XAP file more efficiently. All you need to do is add a single command to your project's post-build events (detailed below) and from then on all your XAP files will be even smaller and quicker to download!

To demonstrate its effectiveness, I've run XapReZip against three test applications, two simple demonstration applications of mine, and the current version of two professional-grade applications you're probably already familiar with. The table below shows the starting XAP file size, the size after running XapReZip, the difference between the two, and the percent difference. (All sizes are in bytes.)

Scenario Starting Size After XapReZip Difference Reduction
New Silverlight Project 3,980 3,202 778 20%
... with DatePicker 73,228 56,513 16,715 23%
... and DataGrid 194,452 151,646 42,806 22%
HtmlTextBlock 12,360 10,312 2,048 17%
SimpleSilverlightXpsViewer 13,879 11,408 2,471 18%
NBC Olympics Video Player 789,523 615,239 174,284 22%
Line Rider 789,496 538,784 250,712 32%

Basically, you can expect to see about a 22% reduction in size for XAP files in general - slightly less for code-intensive XAPs and potentially much more for larger, richer XAPs. For example, it looks like Line Rider could shave a quarter of a megabyte off its download size without breaking a sweat - which is even more compelling given how easy it would be! :)

The complete code for XapReZip.cmd is below. As written, XapReZip assumes that Zip.exe and UnZip.exe will be located in the same directory as XapReZip.cmd (this is easy to change) and that all of the files that are part of the XAP are available in the same directory as the XAP file itself (which just happens to be true after compiling with Visual Studio or MSBuild). For the purposes of this demonstration, I've used Zip 2.32 and UnZip 5.52 from the Info-ZIP group because they're free and have a nice license. Of course, you can use whatever tools you're most comfortable with.

@REM XapReZip - Recompresses XAP files smaller

@REM Invoke as a VS post-build event like so:
@REM C:\XapReZip\XapReZip.cmd $(TargetName).xap

@echo off

REM Define paths to zip.exe and unzip.exe
set ZIPEXE="%~p0zip.exe"
set UNZIPEXE="%~p0unzip.exe"

REM Define paths for intermediate files
set XAP=%1
set XAPDIR=%~p1
set XAPBAK=%1.bak

REM Output a banner message
echo XapReZip: %XAP%

REM Change to XAP file directory
pushd %XAPDIR%

REM Create new XAP file with maximum compression
%UNZIPEXE% -Z -1 %XAP% | %ZIPEXE% -@ -9 -X %XAPZIP%

REM Abort if something went wrong

REM Replace original XAP file with smaller one
copy /y %XAP% %XAPBAK% > NUL
copy /y %XAPZIP% %XAP% > NUL
del %XAPZIP%

REM Output a success message
echo XapReZip: Success


REM Restore previous directory


Adding XapReZip to a Silverlight Project in Visual Studio is easy. Just go to the Project menu, choose Properties (it's the last item), switch to the Build Events tab, and set a post-build event command line like this: C:\XapReZip\XapReZip.cmd $(TargetName).xap. Here's what it looks like in Visual Studio:

Configuring XapReZip as a post-build event in Visual Studio

After you've set that one command, you can forget about it - XapReZip will go to work every time you recompile the application and you'll be able to run and debug it just like always. Except a little smaller. :)

So if you're eager to keep your Silverlight applications as lean as possible, consider adding XapReZip to your project. It'll probably be the easiest 22% savings you get all day!


The layout system lies have become a bit more elaborate [LayoutTransform functionality updated and enhanced for Silverlight 2 Beta 2!]

In the introductory post for LayoutTransformControl, I showed a trivial use case to demonstrate the need for LayoutTransform in some scenarios. I also noted that Silverlight 2 supports only RenderTransform, but went on to demonstrate how it was possible to use RenderTransform to get LayoutTransform behavior. I described how my LayoutTransformControl sample did just that, but implemented only RotateTransform functionality for its initial release. My impression then - as now - is that rotation is easily the most common use of LayoutTransform. However, there are plenty of scenarios where the other Transform subclasses (scale, skew, matrix, etc.) are required, and I wanted to have a solution for them as well.

So I've added full support for arbitrary transformations to LayoutTransformControl along with updating it for Beta 2! (The complete implementation - along with demo and test applications - can be found in LayoutTransformControl.cs in the attached ZIP.)

Where you might previously have written:

<local:LayoutTransformControl Angle="15">
    <TextBlock Text="I am rotated 15 degrees!"/>

You now write:

        <RotateTransform Angle="15"/>
    <TextBlock Text="I am rotated 15 degrees!"/>

Wait a second! That's more typing than before - why is this an improvement? Well, because you can also do this (just as you would on WPF):

        <ScaleTransform ScaleX="1.5" ScaleY="2.5"/>
    <TextBlock Text="I am a little wider and a lot taller!"/>

Or this:

        <MatrixTransform Matrix="-1,0,0,1,0,0"/>
    <TextBlock Text="I am flipped horizontally!"/>

Or even this:

            <ScaleTransform ScaleX="1.5" ScaleY="2.5"/>
            <SkewTransform AngleX="10"/>
            <MatrixTransform Matrix="-1,0,0,1,0,0"/>
            <RotateTransform Angle="15"/>
    <TextBlock Text="I am all of the above - and tilted, too!!"/>

So maybe it's a bit of an improvement, after all... :)

Naturally, I updated my sample application to show off the new capabilities:

LayoutTransformControl Sample Application

And I updated my cross-platform test suite as well (here's the WPF version):

LayoutTransformControl Test Matrix on WPF

LayoutTransformControl should now be just as powerful as WPF's LayoutTransform is. Your application can take advantage of complete LayoutTransform functionality today - even though the Silverlight platform still doesn't officially support LayoutTransform!


  • Improvements to Silverlight in Beta 2 (vs. Beta 1) meant that I was able to remove the lesser of the two Silverlight-specific workarounds present in the Beta 1 code.
  • I removed Button from the test matrix and added two new test cases to cover scenarios where LayoutTransformControl was previously behaving incorrectly. (Unfortunately, the default Button template in Beta 2 still causes the Button to measure/arrange itself incorrectly in some cases. The existing ContentControl test cases already cover correct Button behavior, so there's no loss of coverage.)
  • In WPF, changes to the members of a Transform property (be it an individual Transform or a TransformGroup) automatically cause the Transform property's property changed handler to be invoked (even though OldValue==NewValue). This is a wonderfully elegant way to handle the situation - and unfortunately this behavior isn't present on Silverlight. So LayoutTransformControl needs a way to know when one of its Transform members has been updated and it can't rely on Silverlight to tell it. One solution is to try to create a Binding to the relevant properties of each of the members. Unfortunately, Bindings don't work on Transform-derived classes in Silverlight (my theory: because Transform derives from DependencyObject instead of FrameworkElement where the SetBinding method is implemented). So what I've done is create a set of "Ltc"-prefixed Transform-derived classes that do provide automatic notifications (but still not Binding support - due to the same Silverlight limitation, I suspect). So instead of RotateTransform, you use LtcRotateTransform and get change notifications for free. The "Ltc" Transforms have the same transformation properties (ex: Angle, ScaleX) as their counterparts, so they're simple, plug-compatible replacements - with two caveats: LtcTranslateTransform doesn't exist (because TranslateTransform has no effect during LayoutTransform), and the CenterX/CenterY properties aren't implemented (for the same reason).
  • The "Ltc" Transforms are a pretty good workaround, but you don't have to use them. If the members of the LayoutTransformControl's Transform property never change, then change notification is unnecessary and the standard Transforms can be used without issue. The code in the "Motivation" project (part of the attached solution) demonstrates this approach. If the members of the Transform property do change and you're able to use the "Ltc" transforms, then the right thing should happen automatically. The code in the "Sample" project demonstrates this approach. But if your scenario is such that the members of the Transform property do change and you're unable to use the "Ltc" Transforms, all is not lost! LayoutTransformControl exposes a public TransformUpdated method that you can call to notify it of changes to the members of its Transform property. The code for the test matrix projects uses this last approach.
  • In any kind of project where the goal is to duplicate an existing behavior, it's common to do side-by-side comparisons to find bugs in the new implementation. This is exactly what my WPF test matrix does and it helped me find and fix a number of problems during the development of LayoutTransformControl. However, there typically comes a point at which this comparison process starts revealing differences that turn out to be bugs in the reference implementation. That's usually a pretty good sign that the new implementation is approaching the same level of quality as the old one - and it's a milestone I've hit with LayoutTransformControl. In addition to the "maximal area rectangle" improvement mentioned in the original blog post, LayoutTransformControl exhibits two new, deliberate behavior differences (improvements!) from WPF's LayoutTransform implementation. They're subtle, but they can both be demonstrated in the test matrix. Let me know if you think you've found one! :)
  • The examples above assume the "local" namespace prefix has been mapped to an assembly containing the LayoutTransformControl implementation:


My goal with LayoutTransformControl has always been to address a perceived need. It began life as a bit of an experiment, but by now I've become rather fond of the solution and plan to incorporate it into projects of my own. I hope that if you have a need for LayoutTransform behavior in Silverlight, you'll consider LayoutTransformControl, too!