(1) The file that defines where the excel files get created is CreateFiles.cs in the Creating directory of the ClosedXML_Examples project.
(2) I have created Excel files with over 100,000 rows no problem.
(3) You have to give a valid file name for the SaveAs. @"C:\" is not a file name. Try using @"C:\Filename.xlsx" Also if you are running this via a web application, the server will not access directory like C:\ which is outside of the application location. Try using relative address @".\Filename.xlsx"
(2) I have created Excel files with over 100,000 rows no problem.
(3) You have to give a valid file name for the SaveAs. @"C:\" is not a file name. Try using @"C:\Filename.xlsx" Also if you are running this via a web application, the server will not access directory like C:\ which is outside of the application location. Try using relative address @".\Filename.xlsx"