Как определить ключ добавленной и существующей записи?

private void button1_Click_1(object sender, EventArgs e)
{
  OleDbCommand command = connection.CreateCommand();
  //command.CommandText = "SELECT dateInfo FROM tblDate WHERE dateInfo = @datecyr";
  command.CommandText = "SELECT id FROM tblDate WHERE dateInfo = @datecyr";
  command.Parameters.Add("@datecyr", OleDbType.DBDate);
  command.Parameters[0].Value = cmbDate.Value;
  Object result = command.ExecuteScalar();// Ошибка
  if (result == null)
  {
    command.CommandText = "INSERT INTO tblDate(dateInfo) VALUES(@datecyr)";
    command.Parameters.Add("@datecyr", OleDbType.DBDate);
    command.Parameters[0].Value = cmbDate.Value;
    OleDbCommand cmdSelectId = new OleDbCommand("Select @@Identity", connection);
    result = command.ExecuteNonQuery();
  }
  String str = "INSERT INTO tblData(dataTime, dataF, dataA) ";
  String sTime, sFreq, sAmp;
  for (int i = 0; i < dataGridView1.RowCount - 1; i++)
  {
    sTime = dataGridView1.Rows[i].Cells[0].FormattedValue.ToString();
    sFreq = dataGridView1.Rows[i].Cells[1].FormattedValue.ToString();
    sAmp  = dataGridView1.Rows[i].Cells[2].FormattedValue.ToString();
    command.CommandText = str + "Values(" + "'" + sTime + "'" + ", "
                                               + "'" + sFreq + "'" + ", "
                                               + "'" + sAmp + "'" + ")";
    command.ExecuteNonQuery();
  } // for  
  dataGridView1.RowCount = 1;
}

Object result = command.ExecuteScalar()