Hello Swa,
About the TabControl in MSDN document, the description you can see is below:
 Note   The following events are not raised for the TabControl class unless
there is at least one TabPage in the TabControl.TabPages collection:
Control.Click, Control.DoubleClick, Control.MouseDown, Control.MouseUp,
Control.MouseHover, Control.MouseEnter, Control.MouseLeave and
Control.MouseMove. If there is at least one TabPage in the collection, and
the user interacts with the tab control's header (where the TabPage names
appear), the TabControl raises the appropriate event. However, if the user
interaction is within the ClientRectangle of the tab page, the TabPage
raises the appropriate event.
"Francois Vanderseypen" <netronproject@hotmail.com>
??????:40309dc.0412220252.868be27@posting.google.com...

The TabControl is all Non-Client Area.
WM_NCHITTEST returns HTTRANSPARENT when there is no Tab in the area under
the mouse, so the Tabcontrol does not receive these Mouse events. They are
passed to the underlying control.

To test this just add an eventhandler for Form.Click (assuming the form is
the tabcontrols container) and you will find it fires when you click on the
TabControl.

I haven't tested it, but I would think you can do your dragdrop on the form
(or what ever control is the tabcontrols container) and test whether the
drop point is within the bounds of the tabcontrol.