System.IO.IsolatedStorage

 namespace System.IO.IsolatedStorage {
     public class IsolatedStorageFileStream : FileStream {
+        public override ValueTask DisposeAsync();
+        public override Task FlushAsync(CancellationToken cancellationToken);
+        public override int Read(Span<byte> buffer);
+        public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken);
+        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken));
+        public override void Write(ReadOnlySpan<byte> buffer);
+        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken);
+        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken));
     }
 }