Share a single MongoClient and fix LiteDB TableCollection

src/Core/Grand.Data/LiteDb/LiteDBRepository.cs

@@ -413,7 +413,8 @@ public Task ClearAsync()
     /// </summary>
     public virtual IQueryable<C> TableCollection<C>() where C : class
     {
-        return Database.GetCollection<C>(nameof(T)).Query().ToEnumerable().AsQueryable();
+        //typeof(T).Name, not nameof(T) - the latter is the literal "T"
+        return Database.GetCollection<C>(typeof(T).Name).Query().ToEnumerable().AsQueryable();
     }
 
     #endregion

src/Core/Grand.Infrastructure/Startup/StartupApplication.cs

@@ -51,7 +51,10 @@ private void RegisterDataLayer(IServiceCollection serviceCollection, IConfigurat
                 var mongoUrl = new MongoUrl(connectionString);
                 var databaseName = mongoUrl.DatabaseName;
                 var clientSettings = MongoClientSettings.FromConnectionString(connectionString);
-                serviceCollection.AddScoped(_ => new MongoClient(clientSettings).GetDatabase(databaseName));
+                //the driver expects a single client per connection string - it owns the connection
+                //pool and the cluster monitoring, and is thread-safe
+                serviceCollection.AddSingleton<IMongoClient>(_ => new MongoClient(clientSettings));
+                serviceCollection.AddScoped(sp => sp.GetRequiredService<IMongoClient>().GetDatabase(databaseName));
             }
             else
             {

src/Tests/Grand.Data.Tests/LiteDb/LiteDbRepositoryTests.cs

@@ -552,4 +552,18 @@ await myRepository.UpdateCollectionFieldItem("1", x => x.UserFields, z => z.Key
         Assert.IsTrue(p.UpdatedOnUtc.HasValue);
         Assert.AreEqual("user", p.UpdatedBy);
     }
+
+    [TestMethod]
+    public void TableCollection_ReadsTheEntityCollection()
+    {
+        var myRepository = new LiteDBRepositoryMock<SampleCollection>();
+        myRepository.Insert(new SampleCollection { Id = "1", Name = "Test" });
+        myRepository.Insert(new SampleCollection { Id = "2", Name = "Test2" });
+
+        //reads the collection named after the entity, not one named "T"
+        var result = myRepository.TableCollection<SampleCollection>().ToList();
+
+        Assert.AreEqual(2, result.Count);
+        Assert.IsNotNull(result.FirstOrDefault(x => x.Id == "1"));
+    }
 }