// Load the Excel file Workbook workbook = new Workbook("sample.xlsx"); // Access the first worksheet Worksheet sheet = workbook.Worksheets[0]; // Unlock all cells first Style unlockStyle = workbook.CreateStyle(); unlockStyle.IsLocked = false; StyleFlag styleFlag = new StyleFlag(); styleFlag.Locked = true; sheet.Cells.ApplyStyle(unlockStyle, styleFlag); // Lock specific cells (e.g., A1 and B2) Style lockStyle = workbook.CreateStyle(); lockStyle.IsLocked = true; sheet.Cells["A1"].SetStyle(lockStyle); sheet.Cells["B2"].SetStyle(lockStyle); // Protect the worksheet to enforce the locking sheet.Protect(ProtectionType.All); // Save the modified workbook workbook.Save("output_locked.xlsx");