Adding more SubscribeAsync overloads.

AsyncRx.NET/System.Reactive.Async.Core/System/AsyncObservableExtensions.cs

@@ -9,6 +9,40 @@ namespace System
 {
     public static class AsyncObservableExtensions
     {
+        public static Task<IAsyncDisposable> SubscribeAsync<T>(this IAsyncObservable<T> source, Func<T, Task> onNextAsync)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (onNextAsync == null)
+                throw new ArgumentNullException(nameof(onNextAsync));
+
+            return source.SubscribeAsync(new AsyncObserver<T>(onNextAsync, ex => Task.FromException(ex), () => Task.CompletedTask));
+        }
+
+        public static Task<IAsyncDisposable> SubscribeAsync<T>(this IAsyncObservable<T> source, Func<T, Task> onNextAsync, Func<Exception, Task> onErrorAsync)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (onNextAsync == null)
+                throw new ArgumentNullException(nameof(onNextAsync));
+            if (onErrorAsync == null)
+                throw new ArgumentNullException(nameof(onErrorAsync));
+
+            return source.SubscribeAsync(new AsyncObserver<T>(onNextAsync, onErrorAsync, () => Task.CompletedTask));
+        }
+
+        public static Task<IAsyncDisposable> SubscribeAsync<T>(this IAsyncObservable<T> source, Func<T, Task> onNextAsync, Func<Task> onCompletedAsync)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (onNextAsync == null)
+                throw new ArgumentNullException(nameof(onNextAsync));
+            if (onCompletedAsync == null)
+                throw new ArgumentNullException(nameof(onCompletedAsync));
+
+            return source.SubscribeAsync(new AsyncObserver<T>(onNextAsync, ex => Task.FromException(ex), onCompletedAsync));
+        }
+
         public static Task<IAsyncDisposable> SubscribeAsync<T>(this IAsyncObservable<T> source, Func<T, Task> onNextAsync, Func<Exception, Task> onErrorAsync, Func<Task> onCompletedAsync)
         {
             if (source == null)