Multi Selection TreeView in WPF, the easy way...

I was losing my precious coding time to implement a feature microsoft could do themselves... It's their fault if Genuilder is late ! :p

By the way here is how to use it.
In this example I define an implicit syle for TreeViewItem which set the border in gray when it is selected.

<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="BorderThickness" Value="1"></Setter>
<Style.Triggers>
<Trigger  Property="c:TreeViewExtensions.IsSelected"  Value="True" >
 <Setter Property="BorderBrush" Value="Gray"></Setter>
</Trigger>
</Style.Triggers>
</Style>

...

<TreeView c:TreeViewExtensions.EnableMultiSelect="true"
c:TreeViewExtensions.SelectedItems="{Binding SelectedItems}"
ItemsSource="{Binding Items}"
... />

Here is the TreeViewExtension :


And the sample app :