Adding DelaySubscription.

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

@@ -0,0 +1,74 @@
+// 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.Concurrency;
+using System.Reactive.Disposables;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<TSource> DelaySubscription<TSource>(this IAsyncObservable<TSource> source, TimeSpan dueTime)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return DelaySubscription(source, dueTime, TaskPoolAsyncScheduler.Default);
+        }
+
+        public static IAsyncObservable<TSource> DelaySubscription<TSource>(this IAsyncObservable<TSource> source, TimeSpan dueTime, IAsyncScheduler scheduler)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (scheduler == null)
+                throw new ArgumentNullException(nameof(scheduler));
+
+            return Create<TSource>(async observer =>
+            {
+                var d = new CompositeAsyncDisposable();
+
+                var task = await scheduler.ScheduleAsync(async ct =>
+                {
+                    var inner = await source.SubscribeSafeAsync(observer).ConfigureAwait(false);
+                    await d.AddAsync(inner).ConfigureAwait(false);
+                }, dueTime).ConfigureAwait(false);
+
+                await d.AddAsync(task).ConfigureAwait(false);
+
+                return d;
+            });
+        }
+
+        public static IAsyncObservable<TSource> DelaySubscription<TSource>(this IAsyncObservable<TSource> source, DateTimeOffset dueTime)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return DelaySubscription(source, dueTime, TaskPoolAsyncScheduler.Default);
+        }
+
+        public static IAsyncObservable<TSource> DelaySubscription<TSource>(this IAsyncObservable<TSource> source, DateTimeOffset dueTime, IAsyncScheduler scheduler)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (scheduler == null)
+                throw new ArgumentNullException(nameof(scheduler));
+
+            return Create<TSource>(async observer =>
+            {
+                var d = new CompositeAsyncDisposable();
+
+                var task = await scheduler.ScheduleAsync(async ct =>
+                {
+                    var inner = await source.SubscribeSafeAsync(observer).ConfigureAwait(false);
+                    await d.AddAsync(inner).ConfigureAwait(false);
+                }, dueTime).ConfigureAwait(false);
+
+                await d.AddAsync(task).ConfigureAwait(false);
+
+                return d;
+            });
+        }
+    }
+}