public static DataTable getDataDb(string sqlCommand)
        {
            using (var cnn = dbCon())
            {
                var command = new SqlCommand(sqlCommand, cnn);
                using (var adapter = new SqlDataAdapter {SelectCommand = command})
                {
                    var dataTable = new DataTable();
                    adapter.Fill(dataTable);
                    adapter.Dispose();
                    cnn.Close();
                    return dataTable;
                }
            }
        }

cmbXxx.DataSource = getDataDb(queryString);
cmbXxx.ValueMember = "Id_Otdel";
cmbXxx.DisplayMember = "OtdelName";