Before you add files to the DLL, you need to turn off a default setting that can cause some compile errors for this project.
From the Project
menu, click on "Settings
This brings up the project settings window. There are lots of tabs
and within each tab there can be many more pages of settings.
The first thing you need to do is select "All Configurations
the "Settings For:" drop down combo box in the top left of
the window. By default there are two configuration settings,
Win32 Release and Win32 Debug. Selecting "All Configurations"
allows you to do this only once.
Next, find and select the "C/C++" tab.
you're on this tab, there is a dropdown combo box
called "Category." Select "Precompiled Headers" from the
list. As you can see, each option in the category list changes
what options are visible in the window.
Finally, select "Not using precompiled headers
" and then click OK. Here is a screenshot of what you should see: