diff --git a/MapControl/TileImageLoader.cs b/MapControl/TileImageLoader.cs
index 6af4a58b..59abec08 100644
--- a/MapControl/TileImageLoader.cs
+++ b/MapControl/TileImageLoader.cs
@@ -138,10 +138,11 @@ namespace MapControl
         private void BeginGetTilesAsync(object newTilesList)
         {
             List<Tile> newTiles = (List<Tile>)newTilesList;
-            ImageTileSource imageTileSource = tileLayer.TileSource as ImageTileSource;
 
-            if (imageTileSource != null)
+            if (tileLayer.TileSource is ImageTileSource)
             {
+                ImageTileSource imageTileSource = (ImageTileSource)tileLayer.TileSource;
+
                 newTiles.ForEach(tile =>
                 {
                     Dispatcher.BeginInvoke(DispatcherPriority.Background, (Action)(() => tile.Image = imageTileSource.GetImage(tile.XIndex, tile.Y, tile.ZoomLevel)));
diff --git a/MapControl/TileSource.cs b/MapControl/TileSource.cs
index b7d2c2d9..7da01562 100644
--- a/MapControl/TileSource.cs
+++ b/MapControl/TileSource.cs
@@ -8,6 +8,7 @@ using System.Globalization;
 using System.Text;
 using System.Windows;
 using System.Windows.Media;
+using System.Windows.Media.Imaging;
 
 namespace MapControl
 {
@@ -156,12 +157,16 @@ namespace MapControl
     }
 
     /// <summary>
-    /// Provides the image of a map tile. ImageTileSource bypasses downloading
-    /// and caching of tile images that is performed by TileImageLoader.
+    /// Provides the image of a map tile. ImageTileSource bypasses download and
+    /// cache processing in TileImageLoader. By overriding the GetImage method,
+    /// an application can provide tile images from an arbitrary source.
     /// </summary>
-    public abstract class ImageTileSource : TileSource
+    public class ImageTileSource : TileSource
     {
-        public abstract ImageSource GetImage(int x, int y, int zoomLevel);
+        public virtual ImageSource GetImage(int x, int y, int zoomLevel)
+        {
+            return new BitmapImage(GetUri(x, y, zoomLevel));
+        }
     }
 
     /// <summary>
diff --git a/SampleApps/SampleApplication/ImageTileSource.cs b/SampleApps/SampleApplication/ImageTileSource.cs
deleted file mode 100644
index 7815e32e..00000000
--- a/SampleApps/SampleApplication/ImageTileSource.cs
+++ /dev/null
@@ -1,13 +0,0 @@
-using System.Windows.Media;
-using System.Windows.Media.Imaging;
-
-namespace SampleApplication
-{
-    public class ImageTileSource : MapControl.ImageTileSource
-    {
-        public override ImageSource GetImage(int x, int y, int zoomLevel)
-        {
-            return new BitmapImage(GetUri(x, y, zoomLevel));
-        }
-    }
-}
diff --git a/SampleApps/SampleApplication/MainWindow.xaml b/SampleApps/SampleApplication/MainWindow.xaml
index 781c0f98..6010075d 100644
--- a/SampleApps/SampleApplication/MainWindow.xaml
+++ b/SampleApps/SampleApplication/MainWindow.xaml
@@ -144,7 +144,7 @@
                         
                          <map:TileLayer Name="OSM Uncached" Description="© {y} OpenStreetMap Contributors, CC-BY-SA">
                             <map:TileLayer.TileSource>
-                                <local:ImageTileSource UriFormat="http://{c}.tile.openstreetmap.org/{z}/{x}/{y}.png"/>
+                                <map:ImageTileSource UriFormat="http://{c}.tile.openstreetmap.org/{z}/{x}/{y}.png"/>
                             </map:TileLayer.TileSource>
                         </map:TileLayer>
                     </ComboBox.Items>
diff --git a/SampleApps/SampleApplication/SampleApplication.csproj b/SampleApps/SampleApplication/SampleApplication.csproj
index 1807aac9..f8ae4383 100644
--- a/SampleApps/SampleApplication/SampleApplication.csproj
+++ b/SampleApps/SampleApplication/SampleApplication.csproj
@@ -54,7 +54,6 @@
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>
     </ApplicationDefinition>
-    <Compile Include="ImageTileSource.cs" />
     <Compile Include="Properties\Settings.Designer.cs">
       <AutoGen>True</AutoGen>
       <DesignTimeSharedInput>True</DesignTimeSharedInput>