Allow "refreshing" instances via DatabaseBackedStore

osu.Game/Database/DatabaseBackedStore.cs

@@ -18,6 +18,11 @@ namespace osu.Game.Database
 
         private readonly ThreadLocal<OsuDbContext> queryContext;
 
+        /// <summary>
+        /// Refresh an instance potentially from a diffrent thread with a local context-tracked instance.
+        /// </summary>
+        protected void Refresh<T>(ref T obj) where T : class, IHasPrimaryKey => obj = GetContext().Find<T>(obj.ID);
+
         /// <summary>
         /// Retrieve a shared context for performing lookups (or write operations on the update thread, for now).
         /// </summary>

osu.Game/Database/IHasPrimaryKey.cs

@@ -0,0 +1,10 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+namespace osu.Game.Database
+{
+    public interface IHasPrimaryKey
+    {
+        int ID { get; set; }
+    }
+}

osu.Game/osu.Game.csproj

@@ -282,6 +282,7 @@
     <Compile Include="Beatmaps\Drawables\BeatmapSetCover.cs" />
     <Compile Include="Beatmaps\Drawables\BeatmapSetHeader.cs" />
     <Compile Include="Database\DatabaseContextFactory.cs" />
+    <Compile Include="Database\IHasPrimaryKey.cs" />
     <Compile Include="Migrations\20171019041408_InitialCreate.cs" />
     <Compile Include="Migrations\20171019041408_InitialCreate.Designer.cs">
       <DependentUpon>20171019041408_InitialCreate.cs</DependentUpon>