如何减少C＃中文本框的keypress事件中的数据库往返

Question

In my Windows Application i am using Text_box with List_box. When event fired in keypress event it retrieve the data and listed in listbox

My problem is: For every keypress event hitting the database and application became slower.

How can i reduce the roundtrip the database in keypress event?

---

private void txtVehicleNo_TextChanged(object sender, EventArgs e)
    {
        try
        {
            lstVehicleNo.Visible = true;
            if (!string.IsNullOrEmpty(txtVehicleNo.Text))
            {
                dsResult = oclsBal.GetVhNo(txtVehicleNo.Text);
                if (dsResult.Tables.Count > 0)
                {

                    DataRow dr = dsResult.Tables[0].NewRow();
                    lstVehicleNo.DataSource = dsResult.Tables[0];
                    lstVehicleNo.DisplayMember = "VehicleNo";
                    lstVehicleNo.ValueMember = "VehicleId";
                    lstVehicleNo.SelectedIndex = 0;
                    dsResult.Tables.Clear();
                }

            }
            if (lstVehicleNo.Items.Count == 0)
            {
                lstVehicleNo.Visible = false;
            }
            if (txtVehicleNo.Text.Length == 0)
            {
                lstVehicleNo.Visible = false;
            }
            if (lstVehicleNo.Items.Count == 1)
            {
                if (txtVehicleNo.Text.ToUpper() == lstVehicleNo.Items[0].ToString().ToUpper())
                    lstVehicleNo.Visible = false;
            }

        }
        catch (Exception ex)
        {
            throw ex;
       }

}

Answer 1

Only retrieve the list data after a timeout after the key is pressed, when a key is pressed, reset this timeout. This will mean only getting the data when there is a reasonable enough pause, when the user has stopped typing.

Alternatively use an auto-complete style box that pre-fetches any expected list items.

Answer 2

For the first key-press, get all the records starting with that letter and keep it in cache or local memory and for further key presses you this cache. Since now you have a subset of data in local storage, you should get better performance.