Datatrigger Change ImageBrush source - wpf

Question

Currently am working on a reversi game and this is the ControlTemplate for a Stone on the board , Am using a DataTrigger to see who the Owner is for the Stone to set the button to the appropriate Image , But when I use TargetName on the setter (To the imagebrush wich is imga). I get an Error "Cannot find the Trigger target 'imga'. (The target must appear before any Setters, Triggers, or Conditions that use it.) "
but since I declared this brush before my setters this seems really strange to me. this code is in the app.xaml resources.
Thanks in advance
this is the relevant part of the button
<Style x:Key="0" TargetType="{x:Type Button}">
<Setter Property="Foreground" Value="White" />
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="Height" Value="48"/>
<Setter Property="Width" Value="48" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Ellipse>
<Ellipse.Fill x:Uid="filler">
<ImageBrush x:Name="imga" ImageSource="afbeeldingen/vuur.jpg"/>
</Ellipse.Fill>
</Ellipse>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="#E59400" />
</Trigger>
<DataTrigger Binding="{Binding Owner.Value.ArrayIndex}" Value="0">
<DataTrigger.Setters>
<Setter TargetName="imga" Property="ImageSource" Value="afbeeldingen/vuur.jpg" />
</DataTrigger.Setters>
</DataTrigger>

Answer 1

imga is not a part of your Template, it is a resource, so you cannot change its properties from a trigger. What you have to do is change the Fill property from you Ellipse instead. You would have Something like this :
<ControlTemplate TargetType="{x:Type Button}">
<Ellipse x:Name="myEllipse">
<Ellipse.Fill x:Uid="filler">
<ImageBrush x:Name="imga" ImageSource="afbeeldingen/vuur.jpg"/>
</Ellipse.Fill>
</Ellipse>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="#E59400" />
</Trigger>
<DataTrigger Binding="{Binding Owner.Value.ArrayIndex}" Value="0">
<DataTrigger.Setters>
<Setter TargetName="myEllipse" Property="Fill">
<Setter.Value>
<ImageBrush x:Name="imga" ImageSource="afbeeldingen/vuur.jpg"/>
</Setter.Value>
</Setter>
</DataTrigger.Setters>
</DataTrigger>