public IReadOnlyList<Attachment> GetAttachments( 
   IEnumerable<long> attachmentIDs,
   bool infoOnly
)

public async Task UpdatingAttachments()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    using (FeatureClass landUseCaseFeatureClass = geodatabase.OpenDataset<FeatureClass>("LocalGovernment.GDB.LandUseCase"))
    {
      QueryFilter filter = new QueryFilter { WhereClause = "CASETYPE = 'Rezoning'" };

      using (RowCursor landUseCursor = landUseCaseFeatureClass.Search(filter, false))
      {
        while (landUseCursor.MoveNext())
        {
          using (Feature rezoningUseCase = (Feature)landUseCursor.Current)
          {
            IReadOnlyList<Attachment> rezoningAttachments = rezoningUseCase.GetAttachments();
            IEnumerable<Attachment> filteredAttachments = rezoningAttachments.Where(attachment => !attachment.GetName().Contains("rezoning"));

            foreach (Attachment attachmentToUpdate in filteredAttachments)
            {
              attachmentToUpdate.SetName(attachmentToUpdate.GetName().Replace(".pdf", "Rezoning.pdf"));
              rezoningUseCase.UpdateAttachment(attachmentToUpdate);
            }
          }
        }
      }
    }
  });
}

public async Task DeletingAttachments()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    using (Table inspectionTable = geodatabase.OpenDataset<Table>("luCodeInspection"))
    {
      QueryFilter queryFilter = new QueryFilter { WhereClause = "ACTION = '1st Notice'" };

      using (RowCursor cursor = inspectionTable.Search(queryFilter, false))
      {
        while (cursor.MoveNext())
        {
          using (Row currentRow = cursor.Current)
          {
            IReadOnlyList<Attachment> rowAttachments = currentRow.GetAttachments(null, true);
            IEnumerable<Attachment> attachments = rowAttachments.Where(attachment => attachment.GetContentType().Equals("application/pdf"));

            IReadOnlyList<long> attachmentIDs = attachments.Select(attachment => attachment.GetAttachmentID()) as IReadOnlyList<long>;
            IReadOnlyDictionary<long, Exception> failures = currentRow.DeleteAttachments(attachmentIDs);

            if (failures.Count > 0)
            {
              //process errors
            }
          }
        }
      }
    }
  });
}