Use SemaphoreSlim to ensure cache only remove once

Author: taooceros

Flow.Launcher.Infrastructure/Image/ImageCache.cs

@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using System.Windows.Media;
 
@@ -26,6 +27,7 @@ public class ImageCache
         private const int MaxCached = 50;
         public ConcurrentDictionary<string, ImageUsage> Data { get; private set; } = new ConcurrentDictionary<string, ImageUsage>();
         private const int permissibleFactor = 2;
+        private SemaphoreSlim semaphore = new(1, 1);
 
         public void Initialization(Dictionary<string, int> usage)
         {
@@ -35,8 +37,6 @@ public void Initialization(Dictionary<string, int> usage)
             }
         }
 
-        private volatile bool removing;
-
         public ImageSource this[string path]
         {
             get
@@ -62,15 +62,22 @@ public ImageSource this[string path]
                             }
                 );
 
-                // To prevent the dictionary from drastically increasing in size by caching images, the dictionary size is not allowed to grow more than the permissibleFactor * maxCached size
-                // This is done so that we don't constantly perform this resizing operation and also maintain the image cache size at the same time
-                if (Data.Count > permissibleFactor * MaxCached && !removing)
+                SliceExtra();
+
+                async void SliceExtra()
                 {
-                    removing = true;
-                    // To delete the images from the data dictionary based on the resizing of the Usage Dictionary.
-                    foreach (var key in Data.OrderBy(x => x.Value.usage).Take(Data.Count - MaxCached).Select(x => x.Key))
-                        Data.TryRemove(key, out _);
-                    removing = false;
+                    // To prevent the dictionary from drastically increasing in size by caching images, the dictionary size is not allowed to grow more than the permissibleFactor * maxCached size
+                    // This is done so that we don't constantly perform this resizing operation and also maintain the image cache size at the same time
+                    if (Data.Count > permissibleFactor * MaxCached)
+                    {
+                        await semaphore.WaitAsync();
+                        // To delete the images from the data dictionary based on the resizing of the Usage Dictionary
+                        // Double Check to avoid concurrent remove
+                        if (Data.Count > permissibleFactor * MaxCached)
+                            foreach (var key in Data.OrderBy(x => x.Value.usage).Take(Data.Count - MaxCached).Select(x => x.Key).ToArray())
+                                Data.TryRemove(key, out _);
+                        semaphore.Release();
+                    }
                 }
             }
         }