Adding Finally.

AsyncRx.NET/System.Reactive.Async/System/Reactive/Linq/Operators/Finally.cs

@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information. 
+
+using System.Reactive.Disposables;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<TSource> Finally<TSource>(this IAsyncObservable<TSource> source, Action finallyAction)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (finallyAction == null)
+                throw new ArgumentNullException(nameof(finallyAction));
+
+            return Create<TSource>(async observer =>
+            {
+                var subscription = await source.SubscribeAsync(observer).ConfigureAwait(false);
+
+                return AsyncDisposable.Create(async () =>
+                {
+                    try
+                    {
+                        await subscription.DisposeAsync().ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        finallyAction();
+                    }
+                });
+            });
+        }
+
+        public static IAsyncObservable<TSource> Finally<TSource>(this IAsyncObservable<TSource> source, Func<Task> finallyAction)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (finallyAction == null)
+                throw new ArgumentNullException(nameof(finallyAction));
+
+            return Create<TSource>(async observer =>
+            {
+                var subscription = await source.SubscribeAsync(observer).ConfigureAwait(false);
+
+                return AsyncDisposable.Create(async () =>
+                {
+                    try
+                    {
+                        await subscription.DisposeAsync().ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        await finallyAction().ConfigureAwait(false);
+                    }
+                });
+            });
+        }
+    }
+}