diff --git a/MapControl/Map.Silverlight.WPF.cs b/MapControl/Map.Silverlight.WPF.cs
index 1a0d8b55..5903a450 100644
--- a/MapControl/Map.Silverlight.WPF.cs
+++ b/MapControl/Map.Silverlight.WPF.cs
@@ -10,8 +10,11 @@ namespace MapControl
 {
     public partial class Map
     {
-        partial void Initialize()
+        private Point? mousePosition;
+
+        public Map()
         {
+            MouseWheelZoomChange = 1d;
             MouseWheel += OnMouseWheel;
             MouseLeftButtonDown += OnMouseLeftButtonDown;
             MouseLeftButtonUp += OnMouseLeftButtonUp;
@@ -26,7 +29,7 @@ namespace MapControl
 
         private void OnMouseWheel(object sender, MouseWheelEventArgs e)
         {
-            ZoomMap(e.GetPosition(this), TargetZoomLevel + mouseWheelZoom * Math.Sign(e.Delta));
+            ZoomMap(e.GetPosition(this), TargetZoomLevel + MouseWheelZoomChange * Math.Sign(e.Delta));
         }
 
         private void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
diff --git a/MapControl/Map.WinRT.cs b/MapControl/Map.WinRT.cs
index 9ba36c70..ff913837 100644
--- a/MapControl/Map.WinRT.cs
+++ b/MapControl/Map.WinRT.cs
@@ -11,8 +11,11 @@ namespace MapControl
 {
     public partial class Map
     {
-        partial void Initialize()
+        private Point? mousePosition;
+
+        public Map()
         {
+            MouseWheelZoomChange = 1d;
             ManipulationMode = ManipulationModes.All;
             ManipulationDelta += OnManipulationDelta;
             PointerWheelChanged += OnPointerWheelChanged;
@@ -34,7 +37,7 @@ namespace MapControl
         private void OnPointerWheelChanged(object sender, PointerRoutedEventArgs e)
         {
             var point = e.GetCurrentPoint(this);
-            ZoomMap(point.Position, TargetZoomLevel + mouseWheelZoom * Math.Sign(point.Properties.MouseWheelDelta));
+            ZoomMap(point.Position, TargetZoomLevel + MouseWheelZoomChange * Math.Sign(point.Properties.MouseWheelDelta));
         }
 
         private void OnPointerPressed(object sender, PointerRoutedEventArgs e)
diff --git a/MapControl/Map.cs b/MapControl/Map.cs
index a73f290b..fa11a35f 100644
--- a/MapControl/Map.cs
+++ b/MapControl/Map.cs
@@ -2,12 +2,6 @@
 // Copyright © 2012 Clemens Fischer
 // Licensed under the Microsoft Public License (Ms-PL)
 
-#if WINRT
-using Windows.Foundation;
-#else
-using System.Windows;
-#endif
-
 namespace MapControl
 {
     /// <summary>
@@ -15,20 +9,9 @@ namespace MapControl
     /// </summary>
     public partial class Map : MapBase
     {
-        private double mouseWheelZoom = 1d;
-        private Point? mousePosition;
-
-        public Map()
-        {
-            Initialize();
-        }
-
-        partial void Initialize();
-
-        public double MouseWheelZoom
-        {
-            get { return mouseWheelZoom; }
-            set { mouseWheelZoom = value; }
-        }
+        /// <summary>
+        /// Gets or sets the amount by which the ZoomLevel property changes during a MouseWheel event.
+        /// </summary>
+        public double MouseWheelZoomChange { get; set; }
     }
 }
diff --git a/MapControl/MapBase.cs b/MapControl/MapBase.cs
index 8ed125d3..ee08fb18 100644
--- a/MapControl/MapBase.cs
+++ b/MapControl/MapBase.cs
@@ -124,30 +124,49 @@ namespace MapControl
         /// </summary>
         public event EventHandler ViewportChanged;
 
+        /// <summary>
+        /// Gets or sets the map foreground Brush.
+        /// </summary>
         public Brush Foreground
         {
             get { return (Brush)GetValue(ForegroundProperty); }
             set { SetValue(ForegroundProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a Brush that (when not null) is used as value of the
+        /// Foreground property when TileLayer.HasDarkBackground is false.
+        /// </summary>
         public Brush LightForeground
         {
             get { return (Brush)GetValue(LightForegroundProperty); }
             set { SetValue(LightForegroundProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a Brush that (when not null) is used as value of the
+        /// Foreground property when TileLayer.HasDarkBackground is true.
+        /// </summary>
         public Brush DarkForeground
         {
             get { return (Brush)GetValue(DarkForegroundProperty); }
             set { SetValue(DarkForegroundProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a Brush that (when not null) is used as value of the
+        /// Background property when TileLayer.HasDarkBackground is false.
+        /// </summary>
         public Brush LightBackground
         {
             get { return (Brush)GetValue(LightBackgroundProperty); }
             set { SetValue(LightBackgroundProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a Brush that (when not null) is used as value of the
+        /// Background property when TileLayer.HasDarkBackground is true.
+        /// </summary>
         public Brush DarkBackground
         {
             get { return (Brush)GetValue(DarkBackgroundProperty); }
diff --git a/MapControl/MapControl.Silverlight.csproj b/MapControl/MapControl.Silverlight.csproj
index ef1131e5..0863860f 100644
--- a/MapControl/MapControl.Silverlight.csproj
+++ b/MapControl/MapControl.Silverlight.csproj
@@ -83,7 +83,6 @@
     <Compile Include="MapOverlay.Silverlight.WinRT.cs" />
     <Compile Include="MapPanel.cs" />
     <Compile Include="MapPanel.Silverlight.WinRT.cs" />
-    <Compile Include="MapPolygon.cs" />
     <Compile Include="MapPolyline.cs" />
     <Compile Include="MapPolyline.Silverlight.cs" />
     <Compile Include="MapTransform.cs" />
diff --git a/MapControl/MapItem.WPF.cs b/MapControl/MapItem.WPF.cs
index 6b97f5d9..441f822e 100644
--- a/MapControl/MapItem.WPF.cs
+++ b/MapControl/MapItem.WPF.cs
@@ -21,6 +21,9 @@ namespace MapControl
                 typeof(MapItem), new FrameworkPropertyMetadata(typeof(MapItem)));
         }
 
+        /// <summary>
+        /// Gets a value that indicates if the MapItem is the CurrentItem of the containing items collection.
+        /// </summary>
         public bool IsCurrent
         {
             get { return (bool)GetValue(IsCurrentProperty); }
diff --git a/MapControl/MapItemsControl.WPF.cs b/MapControl/MapItemsControl.WPF.cs
index ff474eb4..4b8daece 100644
--- a/MapControl/MapItemsControl.WPF.cs
+++ b/MapControl/MapItemsControl.WPF.cs
@@ -33,6 +33,10 @@ namespace MapControl
             Items.CurrentChanged += OnCurrentItemChanged;
         }
 
+        /// <summary>
+        /// Gets or sets a Geometry that selects all items that lie inside its fill area,
+        /// i.e. where Geometry.FillContains returns true for the item's viewport position.
+        /// </summary>
         public Geometry SelectionGeometry
         {
             get { return (Geometry)GetValue(SelectionGeometryProperty); }
@@ -99,10 +103,11 @@ namespace MapControl
         private bool IsItemInGeometry(object item, Geometry geometry)
         {
             var container = ContainerFromItem(item);
+            Point? viewportPosition;
 
             return container != null &&
-                container.RenderTransform != null &&
-                geometry.FillContains(new Point(container.RenderTransform.Value.OffsetX, container.RenderTransform.Value.OffsetY));
+                (viewportPosition = MapPanel.GetViewportPosition(container)).HasValue &&
+                geometry.FillContains(viewportPosition.Value);
         }
     }
 }
\ No newline at end of file
diff --git a/MapControl/MapPanel.cs b/MapControl/MapPanel.cs
index fa303776..f267c596 100644
--- a/MapControl/MapPanel.cs
+++ b/MapControl/MapPanel.cs
@@ -31,6 +31,9 @@ namespace MapControl
         public static readonly DependencyProperty LocationProperty = DependencyProperty.RegisterAttached(
             "Location", typeof(Location), typeof(MapPanel), new PropertyMetadata(null, LocationPropertyChanged));
 
+        public static readonly DependencyProperty ViewportPositionProperty = DependencyProperty.RegisterAttached(
+            "ViewportPosition", typeof(Point?), typeof(MapPanel), null);
+
         public static Location GetLocation(UIElement element)
         {
             return (Location)element.GetValue(LocationProperty);
@@ -41,6 +44,11 @@ namespace MapControl
             element.SetValue(LocationProperty, value);
         }
 
+        public static Point? GetViewportPosition(UIElement element)
+        {
+            return (Point?)element.GetValue(ViewportPositionProperty);
+        }
+
         protected override Size MeasureOverride(Size availableSize)
         {
             foreach (UIElement element in Children)
@@ -174,21 +182,28 @@ namespace MapControl
 
         private static void SetViewportPosition(UIElement element, MapBase parentMap, Location location)
         {
-            Transform transform = null;
+            Point? viewportPosition = null;
 
             if (parentMap != null && location != null)
             {
-                Point position = parentMap.LocationToViewportPoint(location);
-                transform = new TranslateTransform { X = position.X, Y = position.Y };
+                viewportPosition = parentMap.LocationToViewportPoint(location);
+                element.SetValue(ViewportPositionProperty, viewportPosition);
+            }
+            else
+            {
+                element.ClearValue(ViewportPositionProperty);
             }
 
             var transformGroup = element.RenderTransform as TransformGroup;
 
             if (transformGroup != null)
             {
-                if (transform == null)
+                var transform = new TranslateTransform();
+
+                if (viewportPosition.HasValue)
                 {
-                    transform = new TranslateTransform();
+                    transform.X = viewportPosition.Value.X;
+                    transform.Y = viewportPosition.Value.Y;
                 }
 
                 var transformIndex = transformGroup.Children.Count - 1;
@@ -203,9 +218,13 @@ namespace MapControl
                     transformGroup.Children.Add(transform);
                 }
             }
-            else if (transform != null)
+            else if (viewportPosition.HasValue)
             {
-                element.RenderTransform = transform;
+                element.RenderTransform = new TranslateTransform
+                {
+                    X = viewportPosition.Value.X,
+                    Y = viewportPosition.Value.Y
+                };
             }
             else
             {
diff --git a/MapControl/MapPolygon.cs b/MapControl/MapPolygon.cs
deleted file mode 100644
index c21e137b..00000000
--- a/MapControl/MapPolygon.cs
+++ /dev/null
@@ -1,14 +0,0 @@
-// XAML Map Control - http://xamlmapcontrol.codeplex.com/
-// Copyright © 2012 Clemens Fischer
-// Licensed under the Microsoft Public License (Ms-PL)
-
-namespace MapControl
-{
-    public class MapPolygon : MapPolyline
-    {
-        protected override bool IsClosed
-        {
-            get { return true; }
-        }
-    }
-}
diff --git a/MapControl/MapPolyline.cs b/MapControl/MapPolyline.cs
index c3be1440..9395d278 100644
--- a/MapControl/MapPolyline.cs
+++ b/MapControl/MapPolyline.cs
@@ -17,23 +17,37 @@ namespace MapControl
     {
         public static readonly DependencyProperty LocationsProperty = DependencyProperty.Register(
             "Locations", typeof(LocationCollection), typeof(MapPolyline),
-            new PropertyMetadata(null, LocationsPropertyChanged));
+            new PropertyMetadata(null, (o, e) => ((MapPolyline)o).UpdateGeometry()));
+
+        public static readonly DependencyProperty IsClosedProperty = DependencyProperty.Register(
+            "IsClosed", typeof(bool), typeof(MapPolyline),
+            new PropertyMetadata(false, (o, e) => ((MapPolyline)o).UpdateGeometry()));
 
         protected PathGeometry Geometry = new PathGeometry();
 
+        /// <summary>
+        /// Gets or sets the locations that define the polyline points.
+        /// </summary>
         public LocationCollection Locations
         {
             get { return (LocationCollection)GetValue(LocationsProperty); }
             set { SetValue(LocationsProperty, value); }
         }
 
-        protected virtual bool IsClosed
+        /// <summary>
+        /// Gets or sets a value that indicates if the polyline is closed, i.e. is a polygon.
+        /// </summary>
+        public bool IsClosed
         {
-            get { return false; }
+            get { return (bool)GetValue(IsClosedProperty); }
+            set { SetValue(IsClosedProperty, value); }
         }
 
-        protected virtual void UpdateGeometry(MapBase parentMap, LocationCollection locations)
+        protected virtual void UpdateGeometry()
         {
+            var parentMap = MapPanel.GetParentMap(this);
+            var locations = Locations;
+
             if (parentMap != null && locations != null && locations.Count > 0)
             {
                 var figure = new PathFigure
@@ -62,13 +76,7 @@ namespace MapControl
 
         void IMapElement.ParentMapChanged(MapBase oldParentMap, MapBase newParentMap)
         {
-            UpdateGeometry(newParentMap, Locations);
-        }
-
-        private static void LocationsPropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
-        {
-            var polyline = (MapPolyline)obj;
-            polyline.UpdateGeometry(MapPanel.GetParentMap(polyline), (LocationCollection)e.NewValue);
+            UpdateGeometry();
         }
     }
 }
diff --git a/MapControl/MapTransform.cs b/MapControl/MapTransform.cs
index 6b28c509..9a9c8ad9 100644
--- a/MapControl/MapTransform.cs
+++ b/MapControl/MapTransform.cs
@@ -11,9 +11,11 @@ using System.Windows;
 namespace MapControl
 {
     /// <summary>
-    /// Defines a normal cylindrical projection. Latitude and longitude values in degrees
-    /// are transformed to cartesian coordinates with origin at latitude = 0 and longitude = 0.
+    /// Defines a normal cylindrical projection. Latitude and longitude values in degrees are
+    /// transformed to cartesian coordinates with origin at latitude = 0 and longitude = 0.
     /// Longitude values are transformed identically to x values in the interval [-180 .. 180].
+    /// Latitude values in the interval [-MaxLatitude .. MaxLatitude] are transformed to y values in
+    /// the interval [-180 .. 180] according to the actual projection, e.g. the Mercator projection.
     /// </summary>
     public abstract class MapTransform
     {
diff --git a/MapControl/MercatorTransform.cs b/MapControl/MercatorTransform.cs
index 0376d463..3a58b812 100644
--- a/MapControl/MercatorTransform.cs
+++ b/MapControl/MercatorTransform.cs
@@ -13,7 +13,7 @@ namespace MapControl
 {
     /// <summary>
     /// Transforms latitude and longitude values in degrees to cartesian coordinates
-    /// according to the Mercator transform.
+    /// according to the Mercator projection.
     /// </summary>
     public class MercatorTransform : MapTransform
     {
diff --git a/MapControl/WinRT/MapControl.WinRT.csproj b/MapControl/WinRT/MapControl.WinRT.csproj
index dbd75e8f..5525621b 100644
--- a/MapControl/WinRT/MapControl.WinRT.csproj
+++ b/MapControl/WinRT/MapControl.WinRT.csproj
@@ -153,9 +153,6 @@
     <Compile Include="..\MapPanel.Silverlight.WinRT.cs">
       <Link>MapPanel.Silverlight.WinRT.cs</Link>
     </Compile>
-    <Compile Include="..\MapPolygon.cs">
-      <Link>MapPolygon.cs</Link>
-    </Compile>
     <Compile Include="..\MapPolyline.cs">
       <Link>MapPolyline.cs</Link>
     </Compile>