.NET：ClosedXMLを利用し、Excelファイルを読み取り専用でデータをインポート

using ClosedXML.Excel;

namespace Service
{
    internal class ImportExcel
    {
        public void ImportMyExcel(string filename)
        {
            try
            {
                // 読み込み専用で開く
                FileStream fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                XLWorkbook workbook = new XLWorkbook(fs);
                IXLWorksheet worksheet = workbook.Worksheet(1);
                IXLCell cell;

                int i = 1;
                while (true)
                {
                    cell = worksheet.Cell(i, 1);
                    if (String.IsNullOrEmpty(cell.Value.ToString())) break;
                    // TODO:業務ロジック
                    i++;
                }
            }
            catch
            {
                throw (new AppBaseException("Error:Read excel file. : " + filename));
            }
        }
    }
}