Silverlight - Add Ellipses to a canvas dynamically with MVVM
I want to add a dynamic number of ellipses to a canvas and set the ellipse position (canvas.top, canvas.left). I tried binding to an ItemsControl but it each item (ellipse) has a container, so I cant set the ellipses position directly. I don't want an items container, I just wan开发者_Go百科t a canvas that contains ellipses.
Can this be done?
Try this - worked for me -- I use it to freely place textblocks on a canvas.
Re: Re: Positioning Items when Canvas is the ItemsPanel of an ItemsControl 02-26-2010 7:17 AM |
There is an alternative simpler solution that does work in silverlight 3.
<Canvas>
<ItemsControl ItemsSource={Binding MyItems}>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Canvas>
<TextBlock Canvas.Left={Binding Left} Canvas.Top={Binding Top} Text={Binding Text} />
</Canvas>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Canvas>
If the MyItems is a list of items that are of a class that has Left, Top and Text public properties, this works fine. I have also tested with Line and Border to draw simple bar graph graphics in silverlight 3.
From the bottom of this post: http://forums.silverlight.net/forums/p/29753/450510.aspx#450510
Combine it with a Silverlight DataTemplateSelector and you can change the objects you draw based on view model properties:
http://www.codeproject.com/KB/silverlight/SLTemplateSelector.aspx
Ordinarily I would say use an ItemsControl
in conjunction with a Canvas
:
<ItemsControl ItemsSource="{Binding Ellipses}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemsContainerStyle>
<Style>
<Setter Property="Canvas.Left" Value="{Binding Left}"/>
<Setter Property="Canvas.Top" Value="{Binding Top}"/>
</Style>
</ItemsControl.ItemsContainerStyle>
</ItemsControl>
But in a display of Silverlight suckiness, the ItemContainerStyle
property does not work on ItemsControl
. It has support in ItemsControl
, but it's not exposed by ItemsControl
itself. Instead, it's up to subclasses of ItemsControl
- such as ListBox
- to expose it. Oh, and those subclasses have to be provided by Microsoft because the functionality is protected internal
, so you can't just subclass ItemsControl
and expose this stuff yourself. :S
So you could use ListBox
instead, possibly by subclassing it and changing its item container to something simpler than a ListBoxItem
. Or you could just use ListBox
directly and fiddle around until the ListBoxItem
s look the way you want them to (i.e. not selected).
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