Here is my treeview code :
<TreeView Name="UIListAddedTaches" Grid.Column="2" Grid.RowSpan="5" Background="#FFE4E4E4" Foreground="Gray">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="SnapsToDevicePixels" Value="True"/>
<Setter Property="BorderThickness" Value="1"/>
<!--working style-->
<!--When skip this 'template' setter , the data are displayed-->
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Border Name="Border" CornerRadius="1" BorderThickness="1">
<Border.BorderBrush>
<SolidColorBrush Color="Red"/>
</Border.BorderBrush>
<Border.Background>
<SolidColorBrush Color="Green" Opacity="0.5" />
</Border.Background>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<DataTemplate>
<Canvas>
<TextBlock Canvas.Bottom="-20" Canvas.Left="570" FontWeight="Bold" Text="{Binding UserID}">
<TextBlock.ToolTip>
<ToolTip Content="{Binding Author}" ContentStringFormat="{}Auteur : {0}" />
</TextBlock.ToolTip>
</TextBlock>
<!--...-->
</Canvas>
</DataTemplate>
</TreeView.ItemTemplate>
</TreeView>
The problem comes cause of the "Template" setter. When I put this style setter, the data are "hidden" by the background : even with the opacity. Datas are still in the list. Doing this in this way in this exemple is overkill but i need to do it like that to apply conditionnal triggers and stuff. A solution to get datas AND template prop ?