support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Expression/Media/IGeometrySourceExtensions.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Windows;
+
+namespace HandyControl.Expression.Media
+{
+    internal static class GeometrySourceExtensions
+    {
+        public static GeometryEffect GetGeometryEffect(this IGeometrySourceParameters parameters)
+        {
+            if (parameters is DependencyObject obj2)
+            {
+                var geometryEffect = GeometryEffect.GetGeometryEffect(obj2);
+                if (geometryEffect != null && obj2.Equals(geometryEffect.Parent)) return geometryEffect;
+            }
+
+            return null;
+        }
+
+        public static double GetHalfStrokeThickness(this IGeometrySourceParameters parameter)
+        {
+            if (parameter.Stroke != null)
+            {
+                var strokeThickness = parameter.StrokeThickness;
+                if (!double.IsNaN(strokeThickness) && !double.IsInfinity(strokeThickness))
+                    return Math.Abs(strokeThickness) / 2.0;
+            }
+
+            return 0.0;
+        }
+    }
+}