Write-protects the worksheet. A user will not be able to modify the worksheet in Excel without entering the specified password. This method does not encrypt the worksheet.

 public void Protect(System.String password)
Public Sub Protect(ByVal password As String)

The password to use to protect the worksheet. If the password is "" or null, the worksheet will be protected without a password.

To further protect your spreadsheet, you can protect the Workbook's structure using the Workbook.Protect() method or password encrypt the file using the Workbook.EncryptPassword property.

ws.Protect("MyPassword");
ws.Protect("MyPassword")