Adding Count and LongCount.

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

@@ -0,0 +1,52 @@
+// 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. 
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<int> Count<TSource>(this IAsyncObservable<TSource> source)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return Create<int>(observer => source.SubscribeAsync(AsyncObserver.Count<TSource>(observer)));
+        }
+    }
+
+    partial class AsyncObserver
+    {
+        public static IAsyncObserver<TSource> Count<TSource>(IAsyncObserver<int> observer)
+        {
+            if (observer == null)
+                throw new ArgumentNullException(nameof(observer));
+
+            var count = 0;
+
+            return Create<TSource>(
+                async x =>
+                {
+                    try
+                    {
+                        checked
+                        {
+                            count++;
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        await observer.OnErrorAsync(ex).ConfigureAwait(false);
+                        return;
+                    }
+                },
+                observer.OnErrorAsync,
+                async () =>
+                {
+                    await observer.OnNextAsync(count).ConfigureAwait(false);
+                    await observer.OnCompletedAsync().ConfigureAwait(false);
+                }
+            );
+        }
+    }
+}

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

@@ -0,0 +1,52 @@
+// 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. 
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<long> LongCount<TSource>(this IAsyncObservable<TSource> source)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return Create<long>(observer => source.SubscribeAsync(AsyncObserver.LongCount<TSource>(observer)));
+        }
+    }
+
+    partial class AsyncObserver
+    {
+        public static IAsyncObserver<TSource> LongCount<TSource>(IAsyncObserver<long> observer)
+        {
+            if (observer == null)
+                throw new ArgumentNullException(nameof(observer));
+
+            var count = 0L;
+
+            return Create<TSource>(
+                async x =>
+                {
+                    try
+                    {
+                        checked
+                        {
+                            count++;
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        await observer.OnErrorAsync(ex).ConfigureAwait(false);
+                        return;
+                    }
+                },
+                observer.OnErrorAsync,
+                async () =>
+                {
+                    await observer.OnNextAsync(count).ConfigureAwait(false);
+                    await observer.OnCompletedAsync().ConfigureAwait(false);
+                }
+            );
+        }
+    }
+}