When outputting an OpenXML format (xlsx) file using GemBox Spreadsheet the sheet dimension element is not included. It is an optional element according to the OpenXML standard, but e.g. Microsoft Excel always writes it. It would be great to output it, so it is easier to find out the used cell range of a worksheet.
Link to the official documentation of the element:
This feature request has been implemented and is available in the latest versions of GemBox.Spreadsheet.