ModifyStyleEx vs. SetExtendStyle

I had wanted to make a ListControl box in a dialog or in a view to have the extended style of LVS_EX_GRIDLINES, LVS_EX_FULLROWSELECT and LVS_EX_CHECKBOXES. I had tried
m_wndListCtrl.ModifyStyleEx(0,LVS_EX_GRIDLINES|LVS_EX_FULLROWSELECT|LVS_EX_CHECKBOXES);


in OnInitDialog() or OnInitialUpdate() but failed. But using SetExtendedStyle works,
DWORD dwStyle=m_wndListCtrl.GetExtendedStyle();
dwStyle|=LVS_EX_GRIDLINES|LVS_EX_FULLROWSELECT|LVS_EX_CHECKBOXES;
m_wndListCtrl.SetExtendedStyle(dwStyle);


Could anybody tell me why? Thanks..:)


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