private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
List <string> dataTableList = ser.queryAllDataTable(connectionStr, this.comboBox1.SelectedItem.ToString().Trim());
this.checkedListBox1.Items.Clear();
foreach (string s in dataTableList)
{
this.checkedListBox1.Items.Add(s);
}
}