Adding CompositeAsyncDisposable.

AsyncRx.NET/System.Reactive.Async/System/Reactive/Disposables/CompositeAsyncDisposable.cs

@@ -0,0 +1,65 @@
+// 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.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Disposables
+{
+    public sealed class CompositeAsyncDisposable : IAsyncDisposable
+    {
+        private readonly AsyncLock gate = new AsyncLock();
+        private readonly List<IAsyncDisposable> disposables = new List<IAsyncDisposable>();
+        private bool disposed;
+
+        public async Task AddAsync(IAsyncDisposable disposable)
+        {
+            if (disposable == null)
+                throw new ArgumentNullException(nameof(disposable));
+
+            using (await gate.LockAsync().ConfigureAwait(false))
+            {
+                if (disposed)
+                {
+                    await disposable.DisposeAsync().ConfigureAwait(false);
+                }
+                else
+                {
+                    disposables.Add(disposable);
+                }
+            }
+        }
+
+        public async Task RemoveAsync(IAsyncDisposable disposable)
+        {
+            if (disposable == null)
+                throw new ArgumentNullException(nameof(disposable));
+
+            using (await gate.LockAsync().ConfigureAwait(false))
+            {
+                if (!disposables.Remove(disposable))
+                    throw new InvalidOperationException("Disposable not found.");
+
+                await disposable.DisposeAsync().ConfigureAwait(false);
+            }
+        }
+
+        public async Task DisposeAsync()
+        {
+            using (await gate.LockAsync().ConfigureAwait(false))
+            {
+                if (disposed)
+                    return;
+
+                disposed = true;
+
+                var tasks = disposables.Select(disposable => disposable.DisposeAsync());
+
+                await Task.WhenAll(tasks);
+            }
+        }
+    }
+}