diff --git a/MBTiles/Shared/MBTileData.cs b/MBTiles/Shared/MBTileData.cs
index c6d00fc8..eb37664f 100644
--- a/MBTiles/Shared/MBTileData.cs
+++ b/MBTiles/Shared/MBTileData.cs
@@ -15,11 +15,28 @@ namespace MapControl.MBTiles
     {
         private readonly SQLiteConnection connection;
 
+        public IDictionary<string, string> Metadata { get; } = new Dictionary<string, string>();
+
         private MBTileData(string file)
         {
             connection = new SQLiteConnection("Data Source=" + Path.GetFullPath(file));
         }
 
+        public void Dispose()
+        {
+            connection.Dispose();
+        }
+
+        public static async Task<MBTileData> CreateAsync(string file)
+        {
+            var tileData = new MBTileData(file);
+
+            await tileData.OpenAsync();
+            await tileData.ReadMetadataAsync();
+
+            return tileData;
+        }
+
         private async Task OpenAsync()
         {
             await connection.OpenAsync();
@@ -35,24 +52,8 @@ namespace MapControl.MBTiles
             }
         }
 
-        public static async Task<MBTileData> CreateAsync(string file)
+        private async Task ReadMetadataAsync()
         {
-            var tileData = new MBTileData(file);
-
-            await tileData.OpenAsync();
-
-            return tileData;
-        }
-
-        public void Dispose()
-        {
-            connection.Dispose();
-        }
-
-        public async Task<IDictionary<string, string>> ReadMetadataAsync()
-        {
-            var metadata = new Dictionary<string, string>();
-
             try
             {
                 using (var command = new SQLiteCommand("select * from metadata", connection))
@@ -61,7 +62,7 @@ namespace MapControl.MBTiles
 
                     while (await reader.ReadAsync())
                     {
-                        metadata[(string)reader["name"]] = (string)reader["value"];
+                        Metadata[(string)reader["name"]] = (string)reader["value"];
                     }
                 }
             }
@@ -69,17 +70,15 @@ namespace MapControl.MBTiles
             {
                 Debug.WriteLine("MBTileData: " + ex.Message);
             }
-
-            return metadata;
         }
 
-        public async Task WriteMetadataAsync(IDictionary<string, string> metaData)
+        public async Task WriteMetadataAsync()
         {
             try
             {
                 using (var command = new SQLiteCommand("insert or replace into metadata (name, value) values (@n, @v)", connection))
                 {
-                    foreach (var keyValue in metaData)
+                    foreach (var keyValue in Metadata)
                     {
                         command.Parameters.AddWithValue("@n", keyValue.Key);
                         command.Parameters.AddWithValue("@v", keyValue.Value);
diff --git a/MBTiles/Shared/MBTileLayer.cs b/MBTiles/Shared/MBTileLayer.cs
index f49ea2d9..91b9ebd5 100644
--- a/MBTiles/Shared/MBTileLayer.cs
+++ b/MBTiles/Shared/MBTileLayer.cs
@@ -36,6 +36,14 @@ namespace MapControl.MBTiles
             set { SetValue(FileProperty, value); }
         }
 
+        /// <summary>
+        /// May be overridden to create a derived MBTileSource that handles other tile formats than png and jpg, e.g. pbf.
+        /// </summary>
+        protected virtual MBTileSource CreateTileSource(MBTileData tileData)
+        {
+            return new MBTileSource(tileData);
+        }
+
         private async Task FilePropertyChanged(string file)
         {
             (TileSource as MBTileSource)?.Dispose();
@@ -48,33 +56,32 @@ namespace MapControl.MBTiles
 
             if (file != null)
             {
-                var tiledata = await MBTileData.CreateAsync(file);
-                var metadata = await tiledata.ReadMetadataAsync();
-                string s;
+                var tileData = await MBTileData.CreateAsync(file);
                 int minZoom;
                 int maxZoom;
+                string s;
 
-                if (metadata.TryGetValue("name", out s))
+                if (tileData.Metadata.TryGetValue("name", out s))
                 {
                     SourceName = s;
                 }
 
-                if (metadata.TryGetValue("description", out s))
+                if (tileData.Metadata.TryGetValue("description", out s))
                 {
                     Description = s;
                 }
 
-                if (metadata.TryGetValue("minzoom", out s) && int.TryParse(s, out minZoom))
+                if (tileData.Metadata.TryGetValue("minzoom", out s) && int.TryParse(s, out minZoom))
                 {
                     MinZoomLevel = minZoom;
                 }
 
-                if (metadata.TryGetValue("maxzoom", out s) && int.TryParse(s, out maxZoom))
+                if (tileData.Metadata.TryGetValue("maxzoom", out s) && int.TryParse(s, out maxZoom))
                 {
                     MaxZoomLevel = maxZoom;
                 }
 
-                TileSource = new MBTileSource(tiledata);
+                TileSource = CreateTileSource(tileData);
             }
         }
     }
diff --git a/MBTiles/Shared/MBTileSource.cs b/MBTiles/Shared/MBTileSource.cs
index c3166c69..2ead69f2 100644
--- a/MBTiles/Shared/MBTileSource.cs
+++ b/MBTiles/Shared/MBTileSource.cs
@@ -12,7 +12,7 @@ using System.Windows.Media;
 
 namespace MapControl.MBTiles
 {
-    public sealed class MBTileSource : TileSource, IDisposable
+    public class MBTileSource : TileSource, IDisposable
     {
         public MBTileData TileData { get; }
 
@@ -23,7 +23,15 @@ namespace MapControl.MBTiles
 
         public void Dispose()
         {
-            TileData.Dispose();
+            Dispose(true);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                TileData.Dispose();
+            }
         }
 
         public override async Task<ImageSource> LoadImageAsync(int x, int y, int zoomLevel)