Add Prepend vs StartWith benchmark

Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/PrependVsStartWtihBenchmark.cs

@@ -0,0 +1,71 @@
+// 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.
+
+#if (CURRENT)
+using System;
+using System.Collections.Generic;
+using System.Reactive.Linq;
+using System.Threading;
+using BenchmarkDotNet.Attributes;
+
+namespace Benchmarks.System.Reactive
+{
+    [MemoryDiagnoser]
+    public class PrependVsStartWtihBenchmark
+    {
+        private int _store;
+
+        [Benchmark(Baseline = true)]
+        public void Prepend()
+        {
+            Observable
+                .Empty<int>()
+                .Prepend(0)
+                .Subscribe(v => Volatile.Write(ref _store, v));
+        }
+
+        [Benchmark]
+        public void Prepend_Create()
+        {
+            Observable
+                .Empty<int>()
+                .Prepend(0);
+        }
+
+
+        static readonly IObservable<int> _prependObservable = Observable.Empty<int>().Prepend(0);
+        [Benchmark]
+        public void Prepend_Subscribe()
+        {
+            _prependObservable
+                .Subscribe(v => Volatile.Write(ref _store, v));
+        }
+
+        [Benchmark]
+        public void StartWith()
+        {
+            Observable
+                .Empty<int>()
+                .StartWith(0)
+                .Subscribe(v => Volatile.Write(ref _store, v));
+        }
+
+        [Benchmark]
+        public void StartWith_Create()
+        {
+            Observable
+                .Empty<int>()
+                .StartWith(0);
+        }
+
+        static readonly IObservable<int> _startWithObservable = Observable.Empty<int>().StartWith(0);
+        [Benchmark]
+        public void StartWith_Subscribe()
+        {
+            _startWithObservable
+                .Subscribe(v => Volatile.Write(ref _store, v));
+        }
+    }
+}
+#endif

Rx.NET/Source/benchmarks/Benchmarks.System.Reactive/Program.cs

@@ -30,6 +30,7 @@ namespace Benchmarks.System.Reactive
                 typeof(ComparisonAsyncBenchmark)
 #if (CURRENT)
                 ,typeof(AppendPrependBenchmark)
+                ,typeof(PrependVsStartWtihBenchmark)
 #endif
             });