Caching RecycleBinSmells

src/Umbraco.Core/Cache/CacheKeys.cs

@@ -17,5 +17,8 @@
         public const string UserAllMediaStartNodesPrefix = "AllMediaStartNodes";
         public const string UserMediaStartNodePathsPrefix = "MediaStartNodePaths";
         public const string UserContentStartNodePathsPrefix = "ContentStartNodePaths";
+        
+        public const string ContentRecycleBinCacheKey = "recycleBin_content";
+        public const string MediaRecycleBinCacheKey = "recycleBin_media";
     }
 }

src/Umbraco.Web/Cache/ContentCacheRefresher.cs

@@ -46,6 +46,7 @@ namespace Umbraco.Web.Cache
         public override void Refresh(JsonPayload[] payloads)
         {
             AppCaches.RuntimeCache.ClearOfType<PublicAccessEntry>();
+            AppCaches.RuntimeCache.ClearByKey(CacheKeys.ContentRecycleBinCacheKey);
 
             var idsRemoved = new HashSet<int>();
             var isolatedCache = AppCaches.IsolatedCaches.GetOrCreate<IContent>();

src/Umbraco.Web/Cache/MediaCacheRefresher.cs

@@ -48,6 +48,7 @@ namespace Umbraco.Web.Cache
             if (anythingChanged)
             {
                 Current.AppCaches.ClearPartialViewCache();
+                AppCaches.RuntimeCache.ClearByKey(CacheKeys.MediaRecycleBinCacheKey);
 
                 var mediaCache = AppCaches.IsolatedCaches.Get<IMedia>();
 

src/Umbraco.Web/Trees/ContentTreeController.cs

@@ -44,6 +44,8 @@ namespace Umbraco.Web.Trees
 
         protected override bool RecycleBinSmells => Services.ContentService.RecycleBinSmells();
 
+        public override string RecycleBinSmellsCacheKey => CacheKeys.ContentRecycleBinCacheKey;
+
         private int[] _userStartNodes;
 
         protected override int[] UserStartNodes

src/Umbraco.Web/Trees/ContentTreeControllerBase.cs

@@ -26,9 +26,11 @@ namespace Umbraco.Web.Trees
 {
     public abstract class ContentTreeControllerBase : TreeController
     {
+        private readonly AppCaches _appCaches;
 
         protected ContentTreeControllerBase(IGlobalSettings globalSettings, IUmbracoContextAccessor umbracoContextAccessor, ISqlContext sqlContext, ServiceContext services, AppCaches appCaches, IProfilingLogger logger, IRuntimeState runtimeState, UmbracoHelper umbracoHelper) : base(globalSettings, umbracoContextAccessor, sqlContext, services, appCaches, logger, runtimeState, umbracoHelper)
         {
+            _appCaches = appCaches;
         }
 
         protected ContentTreeControllerBase()
@@ -148,6 +150,11 @@ namespace Umbraco.Web.Trees
         /// </summary>
         protected abstract bool RecycleBinSmells { get; }
 
+        /// <summary>
+        /// Gets the name of the recycle bin cache key.
+        /// </summary>
+        public abstract string RecycleBinSmellsCacheKey { get; }
+
         /// <summary>
         /// Returns the user's start node for this tree
         /// </summary>
@@ -327,15 +334,29 @@ namespace Umbraco.Web.Trees
                 //and for some reason when there are no dashboards, this parameter is missing  
                 if (IsDialog(queryStrings) == false && id == Constants.System.RootString && queryStrings.HasKey("application"))
                 {
+                    var cache = _appCaches.RuntimeCache;
+                    
+                    var hasChildren = cache.GetCacheItem<bool?>(RecycleBinSmellsCacheKey);
+                    bool recycleBinSmells;
+
+                    if (!(hasChildren is null))
+                    {
+                        recycleBinSmells = (bool) hasChildren;
+                    }
+                    else
+                    {
+                        recycleBinSmells = RecycleBinSmells;
+                        cache.InsertCacheItem<bool>(RecycleBinSmellsCacheKey, () => recycleBinSmells);
+                    }
+
                     nodes.Add(CreateTreeNode(
                         RecycleBinId.ToInvariantString(),
                         id,
                         queryStrings,
                         Services.TextService.Localize("general/recycleBin"),
                         "icon-trash",
-                        RecycleBinSmells,
+                        recycleBinSmells,
                         queryStrings.GetRequiredValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/recyclebin"));
-
                 }
 
                 return nodes;

src/Umbraco.Web/Trees/MediaTreeController.cs

@@ -47,6 +47,7 @@ namespace Umbraco.Web.Trees
         protected override int RecycleBinId => Constants.System.RecycleBinMedia;
 
         protected override bool RecycleBinSmells => Services.MediaService.RecycleBinSmells();
+        public override string RecycleBinSmellsCacheKey => CacheKeys.MediaRecycleBinCacheKey;
 
         private int[] _userStartNodes;
         protected override int[] UserStartNodes