Untitled

Display button on tree item mouseOver
<UserControl.Resources>
     <HierarchicalDataTemplate x:Key="TreeSubjects" ItemsSource="{Binding Path=Children}">
        <StackPanel Orientation="Horizontal" VerticalAlignment="Center">
           <CheckBox x:Name="chbChecked" />
           <TextBlock x:Name="txbSubjectName"
           Text="{Binding Path=SubjectName}" Margin="2,0,2,0"  VerticalAlignment="Center" />
           <Button x:Name="btnProperties" Content="Properties"  Visibility="Collapsed"/>
       </StackPanel>
    </HierarchicalDataTemplate >
</UserControl.Resources>

<sdk:TreeView  x:Name="trTaxonomy" ItemsSource="{Binding TreeSubjects}"
                    ItemTemplate="{StaticResource TreeSubjects}"
                    ItemContainerStyle="{StaticResource SubjectNodeStyle}"
                            />