I have an MFC application written with VC6. I have upgraded it to VS2015 and it builds and runs. The application is a main exe with many DLL's that have dialogs in them.
However the application still looks like it is built with VC6. None of the GUI components have the Windows 7 look and feel, they all still look old style.
How can I make my existing application look more modern?
You should at least add this line to your project, for example add to
stdafx.h
See also Enabling Visual Styles
It gets more complicated for owner draw controls. See this reference: Using Visual Styles with Custom and Owner-Drawn Controls
For ListView and TreeView controls, you can call this function for a more modern look (although it doesn't make any difference in Windows 10)
Also make sure your linker setting
ALLOWISOLATION
is set to 'Yes' otherwise the manifest is not even considered.