long m_nFillStyle;
Remarks
The data member in your control class that stores the control's fill style, for example, solid, transparent, or cross-hatched. If you choose the FILLSTYLE option from the Stock Properties tab in the ATL Object Wizard, the wizard automatically creates this data member in your control class, creates put and get methods for the property, and supports IPropertyNotifySink to automatically notify the container when the property changes.
CComControl Overview | Class Members
See Also CComControl::m_nBackStyle