The AGT (Argentum Tela) series of articles is an effort to do two things. Usually an idea is presented only in its finished form. The first goal is to do some Reality Blogging, to show an idea evolve over time without pulling any punches. The second goal, and the example vehicle for the evolution aspect, is an extensible Design Surface for Silverlight similar to what we have in Visual Studio 2008. This type of application has all sorts of interesting uses. My example is a Home Theater layout tool. Read the entire saga: http://www.damonpayne.com/2008/09/14/RunTimeIsDesignTimeForAGT0.aspx
RC0
As promised, my next task was to make any changes needed to prepare the app so far for working with the RC0 Silverlight release.
Object Tag
The first thing I noticed is that when I tried to run the application I was presented with “Get Silverlight”. I figured the version # had changed, but it was actually the type attribute of the object tag:
<object data="data:application/x-silverlight," type="application/x-silverlight-2" width="100%" height="100%">
<param name="source" value="ClientBin/DamonPayne.HTLayout.xap"/>
<param name="onerror" value="onSilverlightError" />
<param name="background" value="white" />
<a href="http://go.microsoft.com/fwlink/?LinkID=124807" style="text-decoration: none;">
<img src="http://go.microsoft.com/fwlink/?LinkId=108181" alt="Get Microsoft Silverlight" style="border-style: none"/>
</a>
</object>
Note the type is now “application/x-silverlight-2”.
XAML weirdness
The next error I noticed was a seemingly uncatchable error that percolated all the way up to the onSilverlightError JavaScript function.
“Can not set ItemTemplate and DisplayMemberPath simultaneously.”
Looking at the XAML, this makes sense.
<ListBox x:Name="_itemLst" Grid.Row="1" DisplayMemberPath="Name" ItemsSource="{Binding ToolboxItems}" SelectedItem="{Binding Path=SelectedToolboxItem, Mode=TwoWay}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" >
<TextBlock Text="{Binding Name}"
This makes sense, it just didn’t cause an error before. I’m setting DisplayMemberPath in XAML, which is then not used since I’ve provided the entire ItemTemplate. It would be useful if the error told me which XAML file the error is in, but this is a small project so far and future Silverlight developers will be starting out with Silverlight 2 Release.
HitTest missed
At this point I thought I’d better do a Clean Solution just to be safe, and sure enough this turned up another issue. At some point, my DesignSurface.HitTest method (required by IDropTarget) disappeared. The Clean Solution found this out for me. Looking back through my code snapshots taken at the end of each article, it’s been gone for quite some time. This behavior from VS2008/Silverlight Tools is just not ok. This was my last breaking change though. UIElement.HitTest is gone, replaced with a method in VisualTreeHelper:
public IEnumerable<UIElement> HitTest(Point p)
{
return VisualTreeHelper.FindElementsInHostCoordinates(p, LayoutRoot);
}
Moving On
I find now that my Selection code is absolutely broken, but that was under repair anyway.
Source code: Because the code was in a state of flux pending the selection/sizing updates, the next source code will be at the end of AGT[12].