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How to: Open and Save Password-Encrypted Files

  • 3 minutes to read

The Spreadsheet Document API can open and save password encrypted files in binary (.xls, .xlsb) and OpenXml (.xlsx) formats.

Open an Encrypted File

Specify the WorkbookImportOptions.Password property to decrypt a loaded file. The table below lists a chain of events raised if the Password property is not specified or returns an invalid password.

Event Description
Workbook.EncryptedFilePasswordRequest Raised if the Password property is not specified or returns an invalid password. Use the EncryptedFilePasswordRequestEventArgs.Password property to specify a new password.
Workbook.EncryptedFilePasswordCheckFailed Raised if the EncryptedFilePasswordRequestEventArgs.Password is set to an empty or invalid password. Handle this event to obtain the error that led to this event (EncryptedFilePasswordCheckFailedEventArgs.Error) and determine whether to prompt a user for a password (EncryptedFilePasswordCheckFailedEventArgs.TryAgain).
Workbook.InvalidFormatException Occurs when the EncryptedFilePasswordCheckFailedEventArgs.TryAgain property is set to false.

The code sample below shows how to handle the Workbook.EncryptedFilePasswordRequest and Workbook.EncryptedFilePasswordCheckFailed events to prompt users to enter a password. If the user cancels the operation, the Spreadsheet Document API shows an exception message and cancels loading the file.

View Example

static bool IsValid { get; set; }

static void Main(string[] args)
    Workbook workbook = new Workbook();

    workbook.EncryptedFilePasswordRequest += Workbook_EncryptedFilePasswordRequest;
    workbook.EncryptedFilePasswordCheckFailed += Workbook_EncryptedFilePasswordCheckFailed;
    workbook.InvalidFormatException += Workbook_InvalidFormatException;


private static void Workbook_EncryptedFilePasswordRequest(object sender, EncryptedFilePasswordRequestEventArgs e)
    //Prompt the user to enter the password
    Console.WriteLine("Enter password:");
    e.Password = Console.ReadLine();
    e.Handled = true;
    IsValid = true;

private static void Workbook_EncryptedFilePasswordCheckFailed(object sender, EncryptedFilePasswordCheckFailedEventArgs e)
    //Analyze the password error:
    switch (e.Error)

        //If the password is empty, raise the request again
        case SpreadsheetDecryptionError.PasswordRequired:
            Console.WriteLine("You did not enter the password!");
            e.TryAgain = true;
            e.Handled = true;

        //If the password is invalid, ask user whether to continue the operation:
        case SpreadsheetDecryptionError.WrongPassword:
            Console.WriteLine("The password is incorrect. Try Again? (y/n)");
            string answer = Console.ReadLine()?.ToLower();
            if (answer == "y")
                e.TryAgain = true;
                e.Handled = true;

            //If user cancels the operation, show an exception message:
                IsValid = false;

    Program.IsValid = false;

    private static void Workbook_InvalidFormatException(object sender, SpreadsheetInvalidFormatExceptionEventArgs e)
    Console.WriteLine(e.Exception.Message.ToString() + " Press any key to close...");

The Workbook.EncryptedFileIntegrityCheckFailed event occurs if the document did not pass the code verification.

Encrypt a Workbook with a Password

Call the Workbook.SaveDocument method overloads to password-protect the document on save. Use the EncryptionOptions object properties to specify password and protection type. Use the DocumentSettings.Encryption property to access the EncryptionOptions object.

EncryptionSettings encryptionOptions = new EncryptionSettings();
encryptionOptions.Type = EncryptionType.Strong;
encryptionOptions.Password = "12345";

workbook.SaveDocument(fileName, documentFormat, encryptionOptions);