Vista - ItemsCollection that contains generic Visuals? (Canvas.ItemsSource

I'm looking for a control that can auto-populate my canvas with databound
items.

Say I have a Canvas bound this this class:

public class Scene
{
private ObservableCollection<ISprite> _Actors = new
ObservableCollection<ISprite>();
public ObservableCollection<ISprite> Actors
{
get { return _Actors;}
}

public Scene()
{
_Actors.Add(new Sprite1());
_Actors.Add(new Sprite2());
}
}

public interface ISprite
{
double X {get;set;}
double Y {get;set;}
}

public class SpriteBase : ISprite
{
#region ISprite Members
...
#endregion

public SpriteBase(double X, double Y)
{
_X = X;
_Y = Y;
}
}

public class Sprite1 : SpriteBase
{
public Sprite1()
: base(10.0, 10.0)
{
}
}

public class Sprite2 : SpriteBase
{
public Sprite2()
: base(50.0, 50.0)
{
}
}


I want to use DataTemplates and something with an ItemsSource to display the
sprites in my canvas:

<Window.Resources>
<ObjectDataProvider x:Key="TheScene" ObjectType="{x:Type code:Scene}"/>
</Window.Resources>
<Canvas Name="MyCanvas" Width="{Binding Path=ActualWidth}"
Height="{Binding Path=ActualHeight}" DataContext="{StaticResource TheScene}">
<Canvas.Resources>
<DataTemplate DataType="{x:Type code:Sprite1}">
<Rectangle Canvas.Left="{Binding Path=X}" Canvas.Top="{Binding
Path=Y}" Height="10" Width="10" Fill="Red" />
</DataTemplate>
<DataTemplate DataType="{x:Type code:Sprite2}">
<Rectangle Canvas.Left="{Binding Path=X}" Canvas.Top="{Binding
Path=Y}" Height="10" Width="10" Fill="Blue" />
</DataTemplate>
</Canvas.Resources>
<ItemsControl ItemsSource="{Binding Path=Actors}" Height="200"
Width="200" Background="CornflowerBlue">
</ItemsControl>

</Canvas>


The above XAML just ends up with the Rectangles one after another in a list,
the Canvas.Top and Canvas.Left are ignored. Is there a better thing to bind
to?

RyanLeeScheider wrote:

> The above XAML just ends up with the Rectangles one after another in a
> list, the Canvas.Top and Canvas.Left are ignored. Is there a better
> thing to bind to?

This is a common mistake. The problem is that your the items themselves are
hosted in a container which is then put into the canvas, so setting the Canvas.Top/Left
on the datatemplate for the item doesn't make sense. Instead you must set
the ItemContainerStyle[1] property to a style that defines some kind of container
element and put the databound Canvas.Top/Left on it instead.

HTH,
Drew

[1] http://winfx.msdn.microsoft.com/libr...ainerStyle.asp

___________________________________
Drew Marsh
Chief Software Architect
Mimeo.com, Inc. - http://www.mimeo.com
Weblog - http://blog.hackedbrain.com/

I've actually got a follow-up question, how can I apply a style (more
explicitly a DataTrigger in Style.Triggers) to the Items in the ItemsControl.
I tried adding a Style with Style.Triggers to the DataTemplate, and that
gives a runtime error (something annoyingly like DataTemplate.Triggers is
invalid child tag, only Triggers and Resources are allowed..), and adding it
to the Rectangle in my DataTemplate or in my parent Canvas or Windows all
lead to the triggers being ignored. My data classes all properly implement
INotifyPropertyChanged.

The DataTrigger SDK sample has the style in the same Resources block as the
DataTemplates, but this doesn't seem to be working for me. I have a feeling
the DataType for the trigger is the key...

Any thoughts?

RyanLeeScheider wrote:

> I've actually got a follow-up question, how can I apply a style (more
> explicitly a DataTrigger in Style.Triggers) to the Items in the
> ItemsControl.
> I tried adding a Style with Style.Triggers to the DataTemplate, and
> that
> gives a runtime error (something annoyingly like DataTemplate.Triggers
> is
> invalid child tag, only Triggers and Resources are allowed..), and
> adding it to the Rectangle in my DataTemplate or in my parent Canvas
> or Windows all lead to the triggers being ignored. My data classes
> all properly implement INotifyPropertyChanged.
>
> The DataTrigger SDK sample has the style in the same Resources block
> as the DataTemplates, but this doesn't seem to be working for me. I
> have a feeling the DataType for the trigger is the key...

This[1] works for me... or am I misunderstanding your problem?

HTH,
Drew

[1]
<Page xmlns="http://schemas.microsoft.com/winfx/avalon/2005" xmlns:x="http://schemas.microsoft.com/winfx/xaml/2005"
>
<Grid>
<Grid.Resources>
<XmlDataProvider x:Key="data">
<root xmlns="">
<test value="1"/>
<test value="2"/>
<test value="3"/>
</root>
</XmlDataProvider>
</Grid.Resources>
<ItemsControl ItemsSource="{Binding Source={StaticResource data}, XPath=//test}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="tb" Text="{Binding XPath=@value}"/>
<DataTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Trigger.Setters>
<Setter TargetName="tb" Property="FontWeight" Value="Bold"/>
<Setter TargetName="tb" Property="FontSize" Value="50"/>
</Trigger.Setters>
</Trigger>
</DataTemplate.Triggers>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</Page>

I'll have to try that, I didn't have my DataTemplates in
ItemsControl.ItemTemplate, but rather in Canvas.Resources in the parent.

However, I'm also trying to trigger on a change in the bound data object,
not a property of the visual.

For example, assume the data source was more like:

<test value="1" special="false"/>

And I change special to "true" in code, I want to have a trigger defined in
the XAML that changes the FontWeight to bold.

Would I be better off just using a value converter and do something like:

<TextBlock FontWeight={Binding
XPath=@special,Converter=MySpecialToFontWeightConverter} />

?


"Drew Marsh" wrote:


> <DataTemplate>
> <TextBlock x:Name="tb" Text="{Binding XPath=@value}"/>
> <DataTemplate.Triggers>
> <Trigger Property="IsMouseOver" Value="True">
> <Trigger.Setters>
> <Setter TargetName="tb" Property="FontWeight" Value="Bold"/>
> <Setter TargetName="tb" Property="FontSize" Value="50"/>
> </Trigger.Setters>
> </Trigger>
> </DataTemplate.Triggers>
> </DataTemplate>

Hi Ryan,

I would try :

<test value = "0" special= "true"/<

Hahaha ... I don't know if it would work but it's worth giving it a go.

Cheers,

Attellati

--
Attellati


"RyanLeeSchneider" wrote:

>
> I'll have to try that, I didn't have my DataTemplates in
> ItemsControl.ItemTemplate, but rather in Canvas.Resources in the parent.
>
> However, I'm also trying to trigger on a change in the bound data object,
> not a property of the visual.
>
> For example, assume the data source was more like:
>
> <test value="1" special="false"/>
>
> And I change special to "true" in code, I want to have a trigger defined in
> the XAML that changes the FontWeight to bold.
>
> Would I be better off just using a value converter and do something like:
>
> <TextBlock FontWeight={Binding
> XPath=@special,Converter=MySpecialToFontWeightConverter} />
>
> ?
>
>
> "Drew Marsh" wrote:
>
>
> > <DataTemplate>
> > <TextBlock x:Name="tb" Text="{Binding XPath=@value}"/>
> > <DataTemplate.Triggers>
> > <Trigger Property="IsMouseOver" Value="True">
> > <Trigger.Setters>
> > <Setter TargetName="tb" Property="FontWeight" Value="Bold"/>
> > <Setter TargetName="tb" Property="FontSize" Value="50"/>
> > </Trigger.Setters>
> > </Trigger>
> > </DataTemplate.Triggers>
> > </DataTemplate>