support for .NET framework 3.5

Still have bugs

Net35/HandyControlDemo_Net35/UserControl/Styles/TreeViewDemoCtl.xaml

@@ -0,0 +1,12 @@
+<UserControl x:Class="HandyControlDemo.UserControl.TreeViewDemoCtl"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             Background="{DynamicResource RegionBrush}">
+    <TreeView Width="200" Margin="32" ItemsSource="{Binding DataList}">
+        <TreeView.ItemTemplate>
+            <HierarchicalDataTemplate ItemsSource="{Binding DataList}">
+                <TextBlock Text="{Binding Name}"/>
+            </HierarchicalDataTemplate>
+        </TreeView.ItemTemplate>
+    </TreeView>
+</UserControl>