File APIs for Word/Excel/PowerPoint/PDF

  When creating Excel templates for budgets, quotations, or sales reports, you often need users to enter their own data without changing the formulas that calculate the results. For example, a quotation template might allow users to update quantities and unit prices while keeping the total amount formulas protected. If someone accidentally overwrites a formula, the calculation may become incorrect without being immediately noticeable. In C#, you can control which Excel cells remain editable, lock the cells containing formulas, and optionally hide those formulas from the formula bar. This tutorial demonstrates how to create an Excel quotation template where users can modify input values but cannot edit the calculated results. Prerequisites Before getting started, install the required Excel processing library in your C# project. In Visual Studio, go to Tools > NuGet Package Manager > Package Manager Console and run: Install - Package FreeSpire . XLS Alternatively, install it...