Adding ToList.

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

@@ -0,0 +1,30 @@
+// 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;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<IList<TSource>> ToList<TSource>(this IAsyncObservable<TSource> source)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return Create<TSource[]>(observer => source.SubscribeAsync(AsyncObserver.ToArray(observer)));
+        }
+    }
+
+    partial class AsyncObserver
+    {
+        public static IAsyncObserver<TSource> ToList<TSource>(IAsyncObserver<IList<TSource>> observer)
+        {
+            if (observer == null)
+                throw new ArgumentNullException(nameof(observer));
+
+            return Aggregate<TSource, List<TSource>, IList<TSource>>(observer, new List<TSource>(), (xs, x) => { xs.Add(x); return xs; }, xs => xs);
+        }
+    }
+}