Optimize tag persistence

DataLayer/UNTESTED/EfClasses/Book.cs

@@ -123,14 +123,8 @@ namespace DataLayer
             ArgumentValidator.EnsureEnumerableNotNullOrEmpty(newContributors, nameof(newContributors));
 
             // the edge cases of doing local-loaded vs remote-only got weird. just load it
-            if (_contributorsLink == null)
+            if (_contributorsLink is null)
-            {
+				getEntry(context).Collection(s => s.ContributorsLink).Load();
-                ArgumentValidator.EnsureNotNull(context, nameof(context));
-                if (!context.Entry(this).IsKeySet)
-                    throw new InvalidOperationException("Could not add contributors");
-
-                context.Entry(this).Collection(s => s.ContributorsLink).Load();
-            }
 
 			var roleContributions = getContributions(role);
             var isIdentical = roleContributions.Select(c => c.Contributor).SequenceEqual(newContributors);
@@ -140,6 +134,7 @@ namespace DataLayer
             _contributorsLink.RemoveWhere(bc => bc.Role == role);
             addNewContributors(newContributors, role);
         }
+
 		private void addNewContributors(IEnumerable<Contributor> newContributors, Role role)
         {
             byte order = 0;
@@ -155,6 +150,18 @@ namespace DataLayer
                 .ToList();
         #endregion
 
+		private Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry<Book> getEntry(DbContext context)
+		{
+			ArgumentValidator.EnsureNotNull(context, nameof(context));
+
+			var entry = context.Entry(this);
+
+			if (!entry.IsKeySet)
+				throw new InvalidOperationException("Could not load a valid Book from database");
+
+			return entry;
+		}
+
         #region series
         private HashSet<SeriesBook> _seriesLink;
         public IEnumerable<SeriesBook> SeriesLink => _seriesLink?.ToList();
@@ -186,14 +193,8 @@ namespace DataLayer
 
             // our add() is conditional upon what's already included in the collection.
             // therefore if not loaded, a trip is required. might as well just load it
-            if (_seriesLink == null)
+            if (_seriesLink is null)
-            {
+				getEntry(context).Collection(s => s.SeriesLink).Load();
-                ArgumentValidator.EnsureNotNull(context, nameof(context));
-                if (!context.Entry(this).IsKeySet)
-                    throw new InvalidOperationException("Could not add series");
-
-                context.Entry(this).Collection(s => s.SeriesLink).Load();
-            }
 
 			var singleSeriesBook = _seriesLink.SingleOrDefault(sb => sb.Series == series);
             if (singleSeriesBook == null)
@@ -211,8 +212,7 @@ namespace DataLayer
         public void AddSupplementDownloadUrl(string url)
         {
             // supplements are owned by Book, so no need to Load():
-            // OwnsMany: "Can only ever appear on navigation properties of other entity types.
+            //  Are automatically loaded, and can only be tracked by a DbContext alongside their owner.
-            //  Are automatically loaded, and can only be tracked by a DbContext alongside their owner."
 
             ArgumentValidator.EnsureNotNullOrWhiteSpace(url, nameof(url));
 
@@ -233,17 +233,10 @@ namespace DataLayer
 
         public void UpdateCategory(Category category, DbContext context = null)
 		{
-            // since category is never null, nullity means it hasn't been loaded. non null means we're correctly loaded. just overwrite
+			// since category is never null, nullity means it hasn't been loaded
-            if (Category != null)
+			if (Category is null)
-            {
+				getEntry(context).Reference(s => s.Category).Load();
-                Category = category;
-                return;
-            }
 
-            if (context == null)
-                throw new Exception("need context");
-            
-            context.Entry(this).Reference(s => s.Category).Load();
 			Category = category;
         }
 

DataLayer/UNTESTED/TagPersistenceInterceptor.cs

@@ -26,13 +26,13 @@ namespace DataLayer
 
 		private static void persistTags(List<EntityEntry> modifiedEntities)
 		{
-			var tagSets = modifiedEntities
+			var tagsCollection = modifiedEntities
 				.Select(e => e.Entity as UserDefinedItem)
 				// filter by null but NOT by blank. blank is the valid way to show the absence of tags
 				.Where(a => a != null)
+				.Select(t => (t.Book.AudibleProductId, t.Tags))
 				.ToList();
-			foreach (var t in tagSets)
+			FileManager.TagsPersistence.Save(tagsCollection);
-				FileManager.TagsPersistence.Save(t.Book.AudibleProductId, t.Tags);
 		}
 	}
 }

DataLayer/_HowTo- EF Core.txt

@@ -7,15 +7,22 @@ nuget
 Microsoft.EntityFrameworkCore.Tools (needed for using Package Manager Console)
 Microsoft.EntityFrameworkCore.Sqlite
 
-MIGRATIONS require standard, not core
+MIGRATIONS
-using standard instead of core. edit 3 things in csproj
+  require core, not standard
-1of3: pluralize xml TargetFramework tag to TargetFrameworks
+  this can be a problem b/c standard and framework can only reference standard, not core
-2of2: TargetFrameworks from: netstandard2.1
+TO USE MIGRATIONS (core and/or standard)
-to: netcoreapp3.0;netstandard2.1
+  add to csproj
-3of3: add
     <PropertyGroup>
       <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
     </PropertyGroup>
+TO USE MIGRATIONS AS *BOTH* CORE AND STANDARD
+  edit csproj
+    pluralize this xml tag
+      from: TargetFramework
+      to: TargetFrameworks
+    inside of TargetFrameworks
+      from: netstandard2.1
+      to: netcoreapp3.0;netstandard2.1
 
 run. error
 SQLite Error 1: 'no such table: Blogs'.

DataLayer/appsettings.json

@@ -3,7 +3,10 @@
     "LibationContext_sqlserver": "Server=(LocalDb)\\MSSQLLocalDB;Database=DataLayer.LibationContext;Integrated Security=true;",
     "LibationContext": "Data Source=LibationContext.db;Foreign Keys=False;",
 
-    "// on windows sqlite paths accept windows and/or unix slashes": "",
+    "// sqlite notes": "",
+    "// absolute path example": "Data Source=C:/foo/bar/sample.db",
+    "// relative path example": "Data Source=sample.db",
+    "// on windows: sqlite paths accept windows and/or unix slashes": "",
     "MyTestContext": "Data Source=%DESKTOP%/sample.db"
   }
 }

FileManager/UNTESTED/TagsPersistence.cs

@@ -27,10 +27,12 @@ namespace FileManager
 			= Policy.Handle<Exception>()
 			.WaitAndRetry(new[] { TimeSpan.FromMilliseconds(100) });
 
-        public static void Save(string productId, string tags)
+		public static void Save(IEnumerable<(string productId, string tags)> tagsCollection)
 		{
 			ensureCache();
 
+			// on initial reload, there's a huge benefit to adding to cache individually then updating the file only once
+			foreach ((string productId, string tags) in tagsCollection)
 				cache[productId] = tags;
 
 			lock (locker)