Grid controls call CanEditShow internally before creating the editor for a cell. CanEditShow is called after the grid has determined that the field can be edited by calling CanEditModify. 

CanEditShow returns false if the Options property does not indicate that the grid allows editing, or if it indicates that the grid permits row selection. Otherwise, if the Options property indicates that the grid is locked in edit mode, or if the grid has input focus, CanEditShow returns true. If the grid is not locked in edit mode and the grid does not have input focus, CanEditShow returns false. 

CanEditModify 

InplaceEditor 

Options