support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Expression/Drawing/PathGeometryHelper.cs

@@ -0,0 +1,25 @@
+using System.Windows.Media;
+
+namespace HandyControl.Expression.Drawing
+{
+    internal static class PathGeometryHelper
+    {
+        public static bool IsStroked(this PathSegment pathSegment) => pathSegment.IsStroked;
+
+        public static PathGeometry AsPathGeometry(this Geometry original)
+        {
+            if (original == null)
+            {
+                return null;
+            }
+
+            if (!(original is PathGeometry geometry))
+            {
+                return PathGeometry.CreateFromGeometry(original);
+            }
+            return geometry;
+        }
+
+        internal static Geometry FixPathGeometryBoundary(Geometry geometry) => geometry;
+    }
+}