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Protecting Excel Files Programmatically

Data security has become more and more important since the internet spreads the data more quickly than we can imagine. We always use Excel files to store a large amount of the data, which is very important to us in our daily life. Thus, in this blog, we are going to give you a detailed introduction about how to protect Excel files with a password in C#. I searched on NuGet and I am lucky enough to have found free Spire.XLS. It works like a charm, so I’d like to share it with you guys.

This blog introduces

  • How to lock the whole Excel Workbook with the password in C#.
  • How to lock some special Worksheet with the password in C#.
  • How to lock certain cells in the Worksheet in C#.

Please note this library can create or load Excel files independently. Here, Microsoft Excel is only used to view the effect.

Part 1

Protect the whole Excel Workbook with the password.

  1. //create an Excel instance and load the document from file   
  2. Workbookworkbook = newWorkbook();  
  3. workbook.LoadFromFile("sample.xlsx");  
  4. //protect the whole workbook  
  5. workbook.Protect("test");  
  6. workbook.SaveToFile("ProtectedExcel.xlsx", ExcelVersion.Version2010);  
The protected Workbook is given for the reference.

protected

Part 2

Protect only the first worksheet in Excel Workbook.
  1. //create an Excel instance and load the document from file   
  2. Workbookworkbook = newWorkbook();  
  3. workbook.LoadFromFile("sample.xlsx");  
  4. //protect specified worksheet  
  5. workbook.Worksheets[0].Protect("abc", SheetProtectionType.All);  
  6. workbook.SaveToFile("ProtectedWorksheet.xlsx", ExcelVersion.Version2010);  
The protected Worksheet is given for the reference.

protected

Part 3

Lock certain cells in Excel Worksheet.
  1. //create an Excel instance and load the document from file   
  2. Workbookworkbook = newWorkbook();  
  3. workbook.LoadFromFile("sample.xlsx");  
  4. Worksheet sheet = workbook.Worksheets[0];  
  5. //lock certain cells  
  6. workbook.Worksheets[0].Range["A1A15"].Style.Locked = true;  
  7. //unlock certain cells  
  8. workbook.Worksheets[0].Range["B1"].Style.Locked = false;  
  9. sheet.Protect("123", SheetProtectionType.All);  
  10. workbook.SaveToFile("ProtectedExcelCells.xlsx", ExcelVersion.Version2010);  
The protected Excel cells are given for the reference.

protected

Conclusion
Thanks to Spire.XLS, due to which I am able to show you how to protect/encrypt Excel Workbook, Excel Worksheets and certain Excel cells programmatically in C#. I hope, you have gained a deeper understanding of the security in Excel after reading my blog. Besides encrypting Excel file formats with the password, it also supports unlocking and decoding Excel files. Thanks a lot for your reading. Happy coding and have a good day.