From 3f396140b65dda7861be8d0673760a52d5ecb851 Mon Sep 17 00:00:00 2001
From: ClemensF <fischer.clemens@gmail.com>
Date: Fri, 22 Jan 2021 23:00:58 +0100
Subject: [PATCH] Update TileImageLoader.cs

---
 MapControl/Shared/TileImageLoader.cs | 35 +++++++++++++++-------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/MapControl/Shared/TileImageLoader.cs b/MapControl/Shared/TileImageLoader.cs
index 14a9695b..7571e100 100644
--- a/MapControl/Shared/TileImageLoader.cs
+++ b/MapControl/Shared/TileImageLoader.cs
@@ -50,34 +50,26 @@ namespace MapControl
         }
 
         private readonly TileQueue tileQueue = new TileQueue();
-        private Func<Tile, Task> loadTileFunc;
+        private TileSource tileSource;
+        private string cacheName;
         private int taskCount;
 
         /// <summary>
         /// Loads all pending tiles from the tiles collection.
-        /// If tileSource.UriFormat starts with "http" and cacheName is a non-empty string,
+        /// If source.UriFormat starts with "http" and cache is a non-empty string,
         /// tile images will be cached in the TileImageLoader's Cache (if that is not null).
         /// </summary>
-        public void LoadTiles(IEnumerable<Tile> tiles, TileSource tileSource, string cacheName)
+        public void LoadTiles(IEnumerable<Tile> tiles, TileSource source, string cache)
         {
             tileQueue.Clear();
 
+            tileSource = source;
+            cacheName = Cache != null && (bool)source.UriFormat?.StartsWith("http") ? cache : null;
+
             tiles = tiles.Where(tile => tile.Pending);
 
             if (tiles.Any() && tileSource != null)
             {
-                if (Cache != null &&
-                    tileSource.UriFormat != null &&
-                    tileSource.UriFormat.StartsWith("http") &&
-                    !string.IsNullOrEmpty(cacheName))
-                {
-                    loadTileFunc = tile => LoadCachedTileAsync(tile, tileSource, cacheName);
-                }
-                else
-                {
-                    loadTileFunc = tile => LoadTileAsync(tile, tileSource);
-                }
-
                 tileQueue.Enqueue(tiles);
 
                 while (taskCount < Math.Min(tileQueue.Count, MaxLoadTasks))
@@ -91,13 +83,24 @@ namespace MapControl
 
         private async Task LoadTilesFromQueueAsync()
         {
+            // tileSource or cacheName may change after dequeuing a tile
+            var source = tileSource;
+            var cache = cacheName;
+
             while (tileQueue.TryDequeue(out Tile tile))
             {
                 tile.Pending = false;
 
                 try
                 {
-                    await loadTileFunc(tile).ConfigureAwait(false);
+                    if (string.IsNullOrEmpty(cache))
+                    {
+                        await LoadTileAsync(tile, source).ConfigureAwait(false);
+                    }
+                    else
+                    {
+                        await LoadCachedTileAsync(tile, source, cache).ConfigureAwait(false);
+                    }
                 }
                 catch (Exception ex)
                 {