support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Expression/Media/IGeometrySource.cs

@@ -0,0 +1,17 @@
+using System.Windows;
+
+namespace HandyControl.Expression.Media
+{
+    public interface IGeometrySource
+    {
+        bool InvalidateGeometry(InvalidateGeometryReasons reasons);
+
+        bool UpdateGeometry(IGeometrySourceParameters parameters, Rect layoutBounds);
+
+        System.Windows.Media.Geometry Geometry { get; }
+
+        Rect LayoutBounds { get; }
+
+        Rect LogicalBounds { get; }
+    }
+}