Sealing some sinks.

Rx.NET/Source/src/System.Reactive/Linq/Observable/AddRef.cs

@@ -26,7 +26,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<TSource>, IObserver<TSource>
+        private sealed class _ : Sink<TSource>, IObserver<TSource>
         {
             public _(IObserver<TSource> observer, IDisposable cancel)
                 : base(observer, cancel)

Rx.NET/Source/src/System.Reactive/Linq/Observable/AsObservable.cs

@@ -13,10 +13,7 @@ namespace System.Reactive.Linq.ObservableImpl
             _source = source;
         }
 
-        public IObservable<TSource> Eval()
-        {
-            return _source;
-        }
+        public IObservable<TSource> Eval() => _source;
 
         protected override IDisposable Run(IObserver<TSource> observer, IDisposable cancel, Action<IDisposable> setSink)
         {
@@ -25,7 +22,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<TSource>, IObserver<TSource>
+        private sealed class _ : Sink<TSource>, IObserver<TSource>
         {
             public _(IObserver<TSource> observer, IDisposable cancel)
                 : base(observer, cancel)

Rx.NET/Source/src/System.Reactive/Linq/Observable/Average.cs

@@ -20,7 +20,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<double>, IObserver<double>
+        private sealed class _ : Sink<double>, IObserver<double>
         {
             private double _sum;
             private long _count;
@@ -88,7 +88,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<float>, IObserver<float>
+        private sealed class _ : Sink<float>, IObserver<float>
         {
             private double _sum; // NOTE: Uses a different accumulator type (double), conform LINQ to Objects.
             private long _count;
@@ -156,7 +156,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<decimal>, IObserver<decimal>
+        private sealed class _ : Sink<decimal>, IObserver<decimal>
         {
             private decimal _sum;
             private long _count;
@@ -224,7 +224,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<double>, IObserver<int>
+        private sealed class _ : Sink<double>, IObserver<int>
         {
             private long _sum;
             private long _count;
@@ -292,7 +292,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<double>, IObserver<long>
+        private sealed class _ : Sink<double>, IObserver<long>
         {
             private long _sum;
             private long _count;
@@ -360,7 +360,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<double?>, IObserver<double?>
+        private sealed class _ : Sink<double?>, IObserver<double?>
         {
             private double _sum;
             private long _count;
@@ -431,7 +431,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<float?>, IObserver<float?>
+        private sealed class _ : Sink<float?>, IObserver<float?>
         {
             private double _sum; // NOTE: Uses a different accumulator type (double), conform LINQ to Objects.
             private long _count;
@@ -502,7 +502,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<decimal?>, IObserver<decimal?>
+        private sealed class _ : Sink<decimal?>, IObserver<decimal?>
         {
             private decimal _sum;
             private long _count;
@@ -573,7 +573,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<double?>, IObserver<int?>
+        private sealed class _ : Sink<double?>, IObserver<int?>
         {
             private long _sum;
             private long _count;
@@ -644,7 +644,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<double?>, IObserver<long?>
+        private sealed class _ : Sink<double?>, IObserver<long?>
         {
             private long _sum;
             private long _count;

Rx.NET/Source/src/System.Reactive/Linq/Observable/Case.cs

@@ -36,7 +36,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return sink.Run();
         }
 
-        class _ : Sink<TResult>, IObserver<TResult>
+        private sealed class _ : Sink<TResult>, IObserver<TResult>
         {
             private readonly Case<TValue, TResult> _parent;
 

Rx.NET/Source/src/System.Reactive/Linq/Observable/Cast.cs

@@ -20,7 +20,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<TResult>, IObserver<TSource>
+        private sealed class _ : Sink<TResult>, IObserver<TSource>
         {
             public _(IObserver<TResult> observer, IDisposable cancel)
                 : base(observer, cancel)

Rx.NET/Source/src/System.Reactive/Linq/Observable/Collect.cs

@@ -25,7 +25,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return sink;
         }
 
-        class _ : PushToPullSink<TSource, TResult>
+        private sealed class _ : PushToPullSink<TSource, TResult>
         {
             private readonly Collect<TSource, TResult> _parent;
 

Rx.NET/Source/src/System.Reactive/Linq/Observable/Concat.cs

@@ -22,12 +22,9 @@ namespace System.Reactive.Linq.ObservableImpl
             return sink.Run(_sources);
         }
 
-        public IEnumerable<IObservable<TSource>> GetSources()
-        {
-            return _sources;
-        }
+        public IEnumerable<IObservable<TSource>> GetSources() => _sources;
 
-        class _ : ConcatSink<TSource>
+        private sealed class _ : ConcatSink<TSource>
         {
             public _(IObserver<TSource> observer, IDisposable cancel)
                 : base(observer, cancel)

Rx.NET/Source/src/System.Reactive/Linq/Observable/Contains.cs

@@ -26,7 +26,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<bool>, IObserver<TSource>
+        private sealed class _ : Sink<bool>, IObserver<TSource>
         {
             private readonly Contains<TSource> _parent;
 

Rx.NET/Source/src/System.Reactive/Linq/Observable/DelaySubscription.cs

@@ -47,7 +47,7 @@ namespace System.Reactive.Linq.ObservableImpl
             return _source.SubscribeSafe(sink);
         }
 
-        class _ : Sink<TSource>, IObserver<TSource>
+        private sealed class _ : Sink<TSource>, IObserver<TSource>
         {
             public _(IObserver<TSource> observer, IDisposable cancel)
                 : base(observer, cancel)

Rx.NET/Source/src/System.Reactive/Linq/Observable/DoWhile.cs

@@ -31,7 +31,7 @@ namespace System.Reactive.Linq.ObservableImpl
                 yield return _source;
         }
 
-        class _ : ConcatSink<TSource>
+        private sealed class _ : ConcatSink<TSource>
         {
             public _(IObserver<TSource> observer, IDisposable cancel)
                 : base(observer, cancel)