Adding Using and async variants.

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

@@ -0,0 +1,216 @@
+// 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.Disposables;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<TResult> Using<TResult, TResource>(Func<TResource> resourceFactory, Func<TResource, IAsyncObservable<TResult>> observableFactory)
+            where TResource : IDisposable
+        {
+            if (resourceFactory == null)
+                throw new ArgumentNullException(nameof(resourceFactory));
+            if (observableFactory == null)
+                throw new ArgumentNullException(nameof(observableFactory));
+
+            return Create<TResult>(async observer =>
+            {
+                TResource resource;
+                try
+                {
+                    resource = resourceFactory();
+                }
+                catch (Exception ex)
+                {
+                    await observer.OnErrorAsync(ex);
+                    return AsyncDisposable.Nop;
+                }
+
+                IAsyncObservable<TResult> observable;
+                try
+                {
+                    observable = observableFactory(resource);
+                }
+                catch (Exception ex)
+                {
+                    using (resource)
+                    {
+                        await observer.OnErrorAsync(ex);
+                        return AsyncDisposable.Nop;
+                    }
+                }
+
+                var subscription = await observable.SubscribeAsync(observer).ConfigureAwait(false);
+
+                return AsyncDisposable.Create(async () =>
+                {
+                    using (resource)
+                    {
+                        await subscription.DisposeAsync().ConfigureAwait(false);
+                    }
+                });
+            });
+        }
+
+        public static IAsyncObservable<TResult> UsingAsync<TResult, TResource>(Func<Task<TResource>> resourceFactory, Func<TResource, Task<IAsyncObservable<TResult>>> observableFactory)
+            where TResource : IDisposable
+        {
+            if (resourceFactory == null)
+                throw new ArgumentNullException(nameof(resourceFactory));
+            if (observableFactory == null)
+                throw new ArgumentNullException(nameof(observableFactory));
+
+            return Create<TResult>(async observer =>
+            {
+                TResource resource;
+                try
+                {
+                    resource = await resourceFactory().ConfigureAwait(false);
+                }
+                catch (Exception ex)
+                {
+                    await observer.OnErrorAsync(ex);
+                    return AsyncDisposable.Nop;
+                }
+
+                IAsyncObservable<TResult> observable;
+                try
+                {
+                    observable = await observableFactory(resource).ConfigureAwait(false);
+                }
+                catch (Exception ex)
+                {
+                    using (resource)
+                    {
+                        await observer.OnErrorAsync(ex);
+                        return AsyncDisposable.Nop;
+                    }
+                }
+
+                var subscription = await observable.SubscribeAsync(observer).ConfigureAwait(false);
+
+                return AsyncDisposable.Create(async () =>
+                {
+                    using (resource)
+                    {
+                        await subscription.DisposeAsync().ConfigureAwait(false);
+                    }
+                });
+            });
+        }
+
+        public static IAsyncObservable<TResult> UsingAwait<TResult, TResource>(Func<TResource> resourceFactory, Func<TResource, IAsyncObservable<TResult>> observableFactory)
+            where TResource : IAsyncDisposable
+        {
+            if (resourceFactory == null)
+                throw new ArgumentNullException(nameof(resourceFactory));
+            if (observableFactory == null)
+                throw new ArgumentNullException(nameof(observableFactory));
+
+            return Create<TResult>(async observer =>
+            {
+                TResource resource;
+                try
+                {
+                    resource = resourceFactory();
+                }
+                catch (Exception ex)
+                {
+                    await observer.OnErrorAsync(ex);
+                    return AsyncDisposable.Nop;
+                }
+
+                IAsyncObservable<TResult> observable;
+                try
+                {
+                    observable = observableFactory(resource);
+                }
+                catch (Exception ex)
+                {
+                    try
+                    {
+                        await observer.OnErrorAsync(ex);
+                        return AsyncDisposable.Nop;
+                    }
+                    finally
+                    {
+                        await resource.DisposeAsync().ConfigureAwait(false);
+                    }
+                }
+
+                var subscription = await observable.SubscribeAsync(observer).ConfigureAwait(false);
+
+                return AsyncDisposable.Create(async () =>
+                {
+                    try
+                    {
+                        await subscription.DisposeAsync().ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        await resource.DisposeAsync().ConfigureAwait(false);
+                    }
+                });
+            });
+        }
+
+        public static IAsyncObservable<TResult> UsingAwaitAsync<TResult, TResource>(Func<Task<TResource>> resourceFactory, Func<TResource, Task<IAsyncObservable<TResult>>> observableFactory)
+            where TResource : IAsyncDisposable
+        {
+            if (resourceFactory == null)
+                throw new ArgumentNullException(nameof(resourceFactory));
+            if (observableFactory == null)
+                throw new ArgumentNullException(nameof(observableFactory));
+
+            return Create<TResult>(async observer =>
+            {
+                TResource resource;
+                try
+                {
+                    resource = await resourceFactory().ConfigureAwait(false);
+                }
+                catch (Exception ex)
+                {
+                    await observer.OnErrorAsync(ex);
+                    return AsyncDisposable.Nop;
+                }
+
+                IAsyncObservable<TResult> observable;
+                try
+                {
+                    observable = await observableFactory(resource).ConfigureAwait(false);
+                }
+                catch (Exception ex)
+                {
+                    try
+                    {
+                        await observer.OnErrorAsync(ex);
+                        return AsyncDisposable.Nop;
+                    }
+                    finally
+                    {
+                        await resource.DisposeAsync().ConfigureAwait(false);
+                    }
+                }
+
+                var subscription = await observable.SubscribeAsync(observer).ConfigureAwait(false);
+
+                return AsyncDisposable.Create(async () =>
+                {
+                    try
+                    {
+                        await subscription.DisposeAsync().ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        await resource.DisposeAsync().ConfigureAwait(false);
+                    }
+                });
+            });
+        }
+    }
+}