Informs the delegate that an outline view is about to display a cell used to draw the expansion symbol.
Original signature is '- (void)outlineView:(NSOutlineView *)outlineView willDisplayOutlineCell:(id)cell forTableColumn:(NSTableColumn *)tableColumn item:(id)item'
Available in Mac OS X v10.0 and later.

C# | Visual Basic | Visual C++ |
public event NSOutlineView..::..OutlineViewWillDisplayOutlineCellForTableColumnItemEventHandler OutlineViewWillDisplayOutlineCellForTableColumnItem
Public Event OutlineViewWillDisplayOutlineCellForTableColumnItem As NSOutlineView..::..OutlineViewWillDisplayOutlineCellForTableColumnItemEventHandler
public: event NSOutlineView..::..OutlineViewWillDisplayOutlineCellForTableColumnItemEventHandler^ OutlineViewWillDisplayOutlineCellForTableColumnItem { void add (NSOutlineView..::..OutlineViewWillDisplayOutlineCellForTableColumnItemEventHandler^ value); void remove (NSOutlineView..::..OutlineViewWillDisplayOutlineCellForTableColumnItemEventHandler^ value); }

- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)