Adding Case.

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

@@ -0,0 +1,83 @@
+// 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.Concurrency;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IAsyncObservable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IAsyncObservable<TResult>> sources) => Case(selector, sources, Empty<TResult>());
+
+        public static IAsyncObservable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IAsyncObservable<TResult>> sources, IAsyncScheduler scheduler) => Case(selector, sources, Empty<TResult>(scheduler));
+
+        public static IAsyncObservable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IAsyncObservable<TResult>> sources, IAsyncObservable<TResult> defaultSource)
+        {
+            if (selector == null)
+                throw new ArgumentNullException(nameof(selector));
+            if (sources == null)
+                throw new ArgumentNullException(nameof(sources));
+            if (defaultSource == null)
+                throw new ArgumentNullException(nameof(defaultSource));
+
+            return Create<TResult>(observer =>
+            {
+                var source = default(IAsyncObservable<TResult>);
+
+                try
+                {
+                    var value = selector();
+
+                    if (!sources.TryGetValue(value, out source))
+                    {
+                        source = defaultSource;
+                    }
+                }
+                catch (Exception ex)
+                {
+                    return Throw<TResult>(ex).SubscribeAsync(observer);
+                }
+
+                return source.SubscribeSafeAsync(observer);
+            });
+        }
+
+        public static IAsyncObservable<TResult> Case<TValue, TResult>(Func<Task<TValue>> selector, IDictionary<TValue, IAsyncObservable<TResult>> sources) => Case(selector, sources, Empty<TResult>());
+
+        public static IAsyncObservable<TResult> Case<TValue, TResult>(Func<Task<TValue>> selector, IDictionary<TValue, IAsyncObservable<TResult>> sources, IAsyncScheduler scheduler) => Case(selector, sources, Empty<TResult>(scheduler));
+
+        public static IAsyncObservable<TResult> Case<TValue, TResult>(Func<Task<TValue>> selector, IDictionary<TValue, IAsyncObservable<TResult>> sources, IAsyncObservable<TResult> defaultSource)
+        {
+            if (selector == null)
+                throw new ArgumentNullException(nameof(selector));
+            if (sources == null)
+                throw new ArgumentNullException(nameof(sources));
+            if (defaultSource == null)
+                throw new ArgumentNullException(nameof(defaultSource));
+
+            return Create<TResult>(async observer =>
+            {
+                var source = default(IAsyncObservable<TResult>);
+
+                try
+                {
+                    var value = await selector().ConfigureAwait(false);
+
+                    if (!sources.TryGetValue(value, out source))
+                    {
+                        source = defaultSource;
+                    }
+                }
+                catch (Exception ex)
+                {
+                    return await Throw<TResult>(ex).SubscribeAsync(observer).ConfigureAwait(false);
+                }
+
+                return await source.SubscribeSafeAsync(observer).ConfigureAwait(false);
+            });
+        }
+    }
+}