If there is no difference in functionality from before to after you changed the ScrollingMode property, then perhaps the application isn't being rebuilt when you run.
Are you sure that the Configuration for your Solution is set up properly in the Configuration Manager? Try changing the Configuration (or creating a new one) and ensure the 'Build' option is checked for all of the relevant projects. Then go ahead and Clean and Rebuild the solution.
The Configuration Manager, Cleaning and Rebuilding options are all in the "BUILD" menu item in Visual Studio.