Cari tanda tangan Digital di file Xlsm

        
// Set up input Xlsm file
string filePath = "input.xlsm";

// Instantiate Signature for input file
using (GroupDocs.Signature.Signature signature = new GroupDocs.Signature.Signature(filePath))
{
        //Create search options
        DigitalSearchOptions options = new DigitalSearchOptions()
        {
            // specify special search criteria
            Comments = "Approved",
            // specify date range period of signature
            SignDateTimeFrom = new DateTime(year: 2020, month: 01, day: 01),
            SignDateTimeTo = new DateTime(year: 2020, month: 12, day: 31)
        };

        // search for Digital signatures in Xlsm document
        List<DigitalSignature> signatures = signature.Search<DigitalSignature>(options);

        // process signatures which were found                
        foreach (DigitalSignature item in signatures)
        {
            //...
        }
}