Class Libraries & REST APIs for the developers to manipulate & process Files from Word, Excel, PowerPoint, Visio, PDF, CAD & several other categories in Web, Desktop or Mobile apps. Develop & deploy on Windows, Linux, MacOS & Android platforms....first worksheet in the Excel file Worksheet worksheet = workbook...workbook . Worksheets [ 0 ]; worksheet . FreezePanes ( 2 , 2 , 2...