/// <summary>
        /// import from sheet Smlouva
        /// </summary>
        /// <param name="excel_con"></param>
        private void ImportSmlouva(OleDbConnection excel_con)
        {
            DataTable dtExcelData = new DataTable();

            dtExcelData.Columns.AddRange(new DataColumn[6] {
                new DataColumn("Id", typeof(int)),
                new DataColumn("PoskytovatelZdravotnichSluzebId", typeof(int)),
                new DataColumn("PojistovnaId", typeof(int)),
                new DataColumn("TypSmlouvy", typeof(string)),
                new DataColumn("DatumOd", typeof(DateTime)),
                new DataColumn("DatumDo", typeof(DateTime))
            });

            using (OleDbDataAdapter oda = new OleDbDataAdapter("SELECT * FROM [Smlouva$]", excel_con))
            {
                oda.Fill(dtExcelData);

                foreach (DataRow row in dtExcelData.Rows)
                {
                    int     typSmlouvyId = _dataConnector.GetTypSmlouvy((string)row["TypSmlouvy"], (DateTime)row["DatumOd"]).Id;
                    Smlouva smlouva      = new Smlouva()
                    {
                        PoskytovatelZdravotnichSluzebId = (int)row["PoskytovatelZdravotnichSluzebId"],
                        PojistovnaId = (int)row["PojistovnaId"],
                        TypSmlouvyId = typSmlouvyId,
                        DatumOd      = (DateTime)row["DatumOd"],
                        DatumDo      = row.IsNull("DatumDo") ? null : (DateTime?)row["DatumDo"]
                    };

                    _dataConnector.CreateSmlouva(smlouva);
                }
            }
        }