[Modify] Polish it

websocket-sharp/WebSocketFrame.cs

@@ -582,7 +582,8 @@ Extended Payload Length: {7}
       Stream stream,
       WebSocketFrame frame,
       Action<WebSocketFrame> completed,
-      Action<Exception> error)
+      Action<Exception> error
+    )
     {
       var len = frame.IsMasked ? 4 : 0;
       if (len == 0) {
@@ -595,14 +596,16 @@ Extended Payload Length: {7}
       stream.ReadBytesAsync (
         len,
         bytes => {
-          if (bytes.Length != len)
-            throw new WebSocketException (
-              "The masking key of a frame cannot be read from the stream.");
+          if (bytes.Length != len) {
+            var msg = "The masking key of a frame could not be read.";
+            throw new WebSocketException (msg);
+          }
 
           frame._maskingKey = bytes;
           completed (frame);
         },
-        error);
+        error
+      );
     }
 
     private static WebSocketFrame readPayloadData (Stream stream, WebSocketFrame frame)