c# fo-dicom Add Sequence Tag

string filename = "output.dcm";

DicomDataset ds = new DicomDataset(); //Main dataset
ds.Add(DicomTag.SpecificCharacterSet, "ISO_IR 100"); //Add some items
ds.Add(DicomTag.PatientID, "191212121212");

DicomDataset sqContent = new DicomDataset(); //Content of the sequence
sqContent.Add(DicomTag.Modality, "US");
sqContent.Add(DicomTag.ScheduledProcedureStepStartDate, DateTime.Now.Date);

DicomSequence sq = new DicomSequence(DicomTag.ScheduledProcedureStepSequence, sqContent); // Create sequence, add content
ds.Add(sq); //Add sequence to main dataset

DicomFile file = new DicomFile();
file.Dataset.Add(ds); //Add main dataset to DicomFile
file.FileMetaInfo.TransferSyntax = DicomTransferSyntax.ImplicitVRLittleEndian; //Specify transfer syntax
file.Save(filename); //Save file to disk