Adding BehaviorAsyncSubject.

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/BehaviorAsyncSubject.cs

@@ -0,0 +1,171 @@
+// 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.Reactive.Disposables;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Subjects
+{
+    public abstract class BehaviorAsyncSubject<T> : IAsyncSubject<T>
+    {
+        private readonly AsyncLock _gate = new AsyncLock();
+        private readonly List<IAsyncObserver<T>> _observers = new List<IAsyncObserver<T>>();
+        private T _value;
+        private bool _done;
+        private Exception _error;
+
+        public BehaviorAsyncSubject(T value)
+        {
+            _value = value;
+        }
+
+        public T Value
+        {
+            get
+            {
+                var error = _error;
+
+                if (error != null)
+                {
+                    throw error;
+                }
+
+                return _value;
+            }
+        }
+
+        public bool TryGetValue(out T value)
+        {
+            // TODO: support for disposal
+
+            var error = _error;
+
+            if (error != null)
+            {
+                throw error;
+            }
+
+            value = _value;
+            return true;
+        }
+
+        public async Task OnCompletedAsync()
+        {
+            IAsyncObserver<T>[] observers;
+
+            using (await _gate.LockAsync().ConfigureAwait(false))
+            {
+                if (_done || _error != null)
+                {
+                    return;
+                }
+
+                _done = true;
+
+                observers = _observers.ToArray();
+            }
+
+            await OnCompletedAsyncCore(observers).ConfigureAwait(false);
+        }
+
+        protected abstract Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers);
+
+        public async Task OnErrorAsync(Exception error)
+        {
+            if (error == null)
+                throw new ArgumentNullException(nameof(error));
+
+            IAsyncObserver<T>[] observers;
+
+            using (await _gate.LockAsync().ConfigureAwait(false))
+            {
+                if (_done || _error != null)
+                {
+                    return;
+                }
+
+                _error = error;
+
+                observers = _observers.ToArray();
+            }
+
+            await OnErrorAsyncCore(observers, error).ConfigureAwait(false);
+        }
+
+        protected abstract Task OnErrorAsyncCore(IEnumerable<IAsyncObserver<T>> observers, Exception error);
+
+        public async Task OnNextAsync(T value)
+        {
+            IAsyncObserver<T>[] observers;
+
+            using (await _gate.LockAsync().ConfigureAwait(false))
+            {
+                if (_done || _error != null)
+                {
+                    return;
+                }
+
+                _value = value;
+
+                observers = _observers.ToArray();
+            }
+
+            await OnNextAsyncCore(observers, value).ConfigureAwait(false);
+        }
+
+        protected abstract Task OnNextAsyncCore(IEnumerable<IAsyncObserver<T>> observers, T value);
+
+        public async Task<IAsyncDisposable> SubscribeAsync(IAsyncObserver<T> observer)
+        {
+            if (observer == null)
+                throw new ArgumentNullException(nameof(observer));
+
+            bool done;
+            Exception error;
+
+            using (await _gate.LockAsync().ConfigureAwait(false))
+            {
+                done = _done;
+                error = _error;
+
+                if (!done && error == null)
+                {
+                    _observers.Add(observer);
+
+                    await observer.OnNextAsync(_value).ConfigureAwait(false);
+                }
+            }
+
+            if (error != null)
+            {
+                await observer.OnErrorAsync(error).ConfigureAwait(false);
+
+                return AsyncDisposable.Nop;
+            }
+            else if (done)
+            {
+                await observer.OnCompletedAsync().ConfigureAwait(false);
+
+                return AsyncDisposable.Nop;
+            }
+
+            return AsyncDisposable.Create(() =>
+            {
+                lock (_gate)
+                {
+                    var i = _observers.LastIndexOf(observer);
+
+                    if (i >= 0)
+                    {
+                        _observers.RemoveAt(i);
+                    }
+                }
+
+                return Task.CompletedTask;
+            });
+        }
+    }
+}

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/ConcurrentAsyncAsyncSubject.cs

@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 
 namespace System.Reactive.Subjects
 {
-    public class ConcurrentAsyncAsyncSubject<T> : AsyncAsyncSubject<T>
+    public sealed class ConcurrentAsyncAsyncSubject<T> : AsyncAsyncSubject<T>
     {
         protected override Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers) => Task.WhenAll(observers.Select(observer => observer.OnCompletedAsync()));
 

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/ConcurrentBehaviorAsyncSubject.cs

@@ -0,0 +1,24 @@
+// 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.Tasks;
+
+namespace System.Reactive.Subjects
+{
+    public sealed class ConcurrentBehaviorAsyncSubject<T> : BehaviorAsyncSubject<T>
+    {
+        public ConcurrentBehaviorAsyncSubject(T value)
+            : base(value)
+        {
+        }
+
+        protected override Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers) => Task.WhenAll(observers.Select(observer => observer.OnCompletedAsync()));
+
+        protected override Task OnErrorAsyncCore(IEnumerable<IAsyncObserver<T>> observers, Exception error) => Task.WhenAll(observers.Select(observer => observer.OnErrorAsync(error)));
+
+        protected override Task OnNextAsyncCore(IEnumerable<IAsyncObserver<T>> observers, T value) => Task.WhenAll(observers.Select(observer => observer.OnNextAsync(value)));
+    }
+}

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/ConcurrentSimpleAsyncSubject.cs

@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 
 namespace System.Reactive.Subjects
 {
-    public class ConcurrentSimpleAsyncSubject<T> : SimpleAsyncSubject<T>
+    public sealed class ConcurrentSimpleAsyncSubject<T> : SimpleAsyncSubject<T>
     {
         protected override Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers) => Task.WhenAll(observers.Select(observer => observer.OnCompletedAsync()));
 

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/SequentialAsyncAsyncSubject.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 
 namespace System.Reactive.Subjects
 {
-    public class SequentialAsyncAsyncSubject<T> : AsyncAsyncSubject<T>
+    public sealed class SequentialAsyncAsyncSubject<T> : AsyncAsyncSubject<T>
     {
         protected override async Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers)
         {

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/SequentialBehaviorAsyncSubject.cs

@@ -0,0 +1,41 @@
+// 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.Threading.Tasks;
+
+namespace System.Reactive.Subjects
+{
+    public sealed class SequentialBehaviorAsyncSubject<T> : BehaviorAsyncSubject<T>
+    {
+        public SequentialBehaviorAsyncSubject(T value)
+            : base(value)
+        {
+        }
+
+        protected override async Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers)
+        {
+            foreach (var observer in observers)
+            {
+                await observer.OnCompletedAsync().ConfigureAwait(false);
+            }
+        }
+
+        protected override async Task OnErrorAsyncCore(IEnumerable<IAsyncObserver<T>> observers, Exception error)
+        {
+            foreach (var observer in observers)
+            {
+                await observer.OnErrorAsync(error).ConfigureAwait(false);
+            }
+        }
+
+        protected override async Task OnNextAsyncCore(IEnumerable<IAsyncObserver<T>> observers, T value)
+        {
+            foreach (var observer in observers)
+            {
+                await observer.OnNextAsync(value).ConfigureAwait(false);
+            }
+        }
+    }
+}

AsyncRx.NET/System.Reactive.Async.Subjects/System/Reactive/Subjects/SequentialSimpleAsyncSubject.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 
 namespace System.Reactive.Subjects
 {
-    public class SequentialSimpleAsyncSubject<T> : SimpleAsyncSubject<T>
+    public sealed class SequentialSimpleAsyncSubject<T> : SimpleAsyncSubject<T>
     {
         protected override async Task OnCompletedAsyncCore(IEnumerable<IAsyncObserver<T>> observers)
         {