Address PR feedback

dotnet · Sep 10, 2016 · 119c770 · 119c770
1 parent 7d41d78
commit 119c770
Showing 1 changed file with 14 additions and 11 deletions.
diff --git a/src/System.IO.FileSystem/src/System/IO/Win32FileStream.cs b/src/System.IO.FileSystem/src/System/IO/Win32FileStream.cs
@@ -1764,22 +1764,25 @@ private async Task AsyncModeCopyToAsync(Stream destination, int bufferSize, Canc
                 // whatever read operation may currently be in progress, if there is one.  It's possible the cancellation
                 // request could come in between operations, in which case we flag that with explicit calls to ThrowIfCancellationRequested
                 // in the read/write copy loop.
-                cancellationReg = cancellationToken.Register(s =>
+                if (cancellationToken.CanBeCanceled)
                 {
-                    var innerAwaitable = (AsyncCopyToAwaitable)s;
-                    unsafe
+                    cancellationReg = cancellationToken.Register(s =>
                     {
-                        lock (innerAwaitable.CancellationLock) // synchronize with cleanup of the overlapped
+                        var innerAwaitable = (AsyncCopyToAwaitable)s;
+                        unsafe
                         {
-                            if (innerAwaitable._nativeOverlapped != null)
-                            {
-                                // Try to cancel the I/O.  We ignore the return value, as cancellation is opportunistic and we
-                                // don't want to fail the operation because we couldn't cancel it.
-                                Interop.mincore.CancelIoEx(innerAwaitable._fileStream._handle, innerAwaitable._nativeOverlapped);
+                            lock (innerAwaitable.CancellationLock) // synchronize with cleanup of the overlapped
+                        {
+                                if (innerAwaitable._nativeOverlapped != null)
+                                {
+                                    // Try to cancel the I/O.  We ignore the return value, as cancellation is opportunistic and we
+                                    // don't want to fail the operation because we couldn't cancel it.
+                                    Interop.mincore.CancelIoEx(innerAwaitable._fileStream._handle, innerAwaitable._nativeOverlapped);
+                                }
                             }
                         }
-                    }
-                }, readAwaitable);
+                    }, readAwaitable);
+                }
 
                 // Repeatedly read from this FileStream and write the results to the destination stream.
                 while (true)