Vanquish the curse of transform async, but for List now (#612)

Co-authored-by: Tomáš Filip <tomas.filip@meac.cz>
reactivemarbles · Jun 25, 2022 · 4054f13 · 4054f13
1 parent 9e17d5e
commit 4054f13
Showing 1 changed file with 11 additions and 2 deletions.
diff --git a/src/DynamicData/List/Internal/TransformAsync.cs b/src/DynamicData/List/Internal/TransformAsync.cs
@@ -38,12 +38,21 @@ public IObservable<IChangeSet<TDestination>> Run()
             observer =>
             {
                 var state = new ChangeAwareList<TransformedItemContainer>();
+                var asyncLock = new SemaphoreSlim(1, 1);
 
                 return _source.Select(
                     async changes =>
                     {
-                        await Transform(state, changes).ConfigureAwait(false);
-                        return state;
+                        try
+                        {
+                            await asyncLock.WaitAsync().ConfigureAwait(false);
+                            await Transform(state, changes).ConfigureAwait(false);
+                            return state;
+                        }
+                        finally
+                        {
+                            asyncLock.Release();
+                        }
                     }).Select(tasks => tasks.ToObservable()).SelectMany(items => items).Select(
                     transformed =>
                     {