Digital проверка на подписи за Xlsx файлове

        
// Set up input Xlsx file
string filePath = "input.xlsx";

// Instantiate Signature for input file
using (GroupDocs.Signature.Signature signature = new GroupDocs.Signature.Signature(filePath))
{
        //Provide verification options
        DigitalVerifyOptions options = new DigitalVerifyOptions()
        {
            // Digital signature comment
            Comments = "Approved by co-owner",
            // specify period of signatures
            SignDateTimeFrom = new DateTime(year: 2021, month: 01, day: 01),
            SignDateTimeTo = new DateTime(year: 2022, month: 12, day: 31)
        };

        // Verify document signatures
        VerificationResult result = signature.Verify(options);

        //process result
        if (result.IsValid)
        {
            //..
        }
}