数据库中Winform中的textchange事件上的动态自动完成文本框

Question

how can achieve dynamic auto complete textbox in c# winform?

for example ,in my application have a textbox named txtbox_mobileno. i wanna bind mobile number(from database table named customer) with txtbox_mobileno. the table customer have more than 100,000 records .client want suggestion list while typing mobile number in application .

so i tried to implement following code on textchanged event

if (txtbox_mobileno.TextLength >3)
{

cmd.CommandText = "SELECT  TOP 20 MobileNo FROM Customer WHERE MobileNo LIKE'" + txtbox_mobileno.Text+"%'";
SqlDataReader dr;
dr = RunSqlReturnDR(cmd);//return value
 if (dr.HasRows)
 {
    while (dr.Read())
    {
   C.Add(dr[0].ToString()); //AutoCompleteStringCollection C = new AutoCompleteStringCollection();
     }
  }
 dr.Close();
 txtbox_mobileno.AutoCompleteMode = AutoCompleteMode.Suggest;
 txtbox_mobileno.AutoCompleteSource = AutoCompleteSource.CustomSource;
 txtbox_mobileno.AutoCompleteCustomSource = C;
}

i want to show the suggestion list only if text box have more than 3 letters when tried to bind on load event, it took around 5 minutes to bind data with textbox suggestion list ,

Sql server query execution time was only 3 seconds.

is there any fastest way to overcome this issue?

Answer 1

I am not sure if you are able to grab all mobile numbers at the beginning of your app or at least when your data entry form loads up, but if so, it may be easier to load all of the numbers into buckets with the first three characters being the key for the list of numbers. Even if you had 1,000,000 numbers, you are only talking around 30 MB of data (assuming I did my math correctly), so you shouldn't have any issues in that regard. You could do something like this to build your buckets. As an aside, I also have no idea how many numbers you get that have the same first three digits, so I may be building very large autocomplete lists in this code which would be another problem. Your code only pulled back the top 20, you could modify this code to only keep the first 20 or something like that.

var buckets = new Dictionary<string, List<string>>();
cmd.CommandText = "SELECT MobileNo FROM Customer";
SqlDataReader dr = RunSqlReturnDR(cmd);
if (dr.HasRows)
{
    while (dr.Read())
    {
        var number = dr[0].ToString();
        var key = number.Substring(0, 3);
        List<string> numbers = null;
        if(!buckets.TryGetValue(key, out numbers))
        {
            numbers = new List<string>();                 
        }
        numbers.Add(number);
    }
}
dr.Close();

Then in your event handler you just need to do something like this:

if (txtbox_mobileno.Text.Length == 3)
{
    List<string> numbers;
    if (_buckets.TryGetValue(txtbox_mobileno.Text, out numbers)
    {
        var ac = new AutoCompleteStringCollection();
        ac.AddRange(numbers.ToArray());
        txtbox_mobileno.AutoCompleteMode = AutoCompleteMode.Suggest;
        txtbox_mobileno.AutoCompleteSource = AutoCompleteSource.CustomSource;
        txtbox_mobileno.AutoCompleteCustomSource = ac;
    }
}

Other ways you could potentially enhance this would be to add an order by in the query where you get the numbers, then you should be able to walk the values and just create a new list when you hit a change in the first three digits. That would make it easier to build a dictionary of arrays rather than a dictionary of lists, which would then help in your autocomplete box. I also haven't written a lot of DB code in a while, so I just kept the code you posted for getting the data out of the database. It is possible that there may be better ways to read the data from the database.

Answer 2

Try use a timer to fire query, and a Thread to execute, see:

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        timer1.Enabled = false;
        timer1.Enabled = true;
    }

    private void timer1_Tick(object sender, EventArgs e)
    {
        timer1.Enabled = false;

        string filter = txtbox_mobileno.Text;

        Thread t = new Thread(() => {

            cmd.CommandText = "SELECT  TOP 20 MobileNo FROM Customer WHERE MobileNo LIKE '" + filter + "%'";
            SqlDataReader dr;
            dr = RunSqlReturnDR(cmd);//return value
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    C.Add(dr[0].ToString()); //AutoCompleteStringCollection C = new AutoCompleteStringCollection();
                }
            }

            dr.Close();

            txtbox_mobileno.Invoke((MethodInvoker)delegate {
                txtbox_mobileno.AutoCompleteMode = AutoCompleteMode.Suggest;
                txtbox_mobileno.AutoCompleteSource = AutoCompleteSource.CustomSource;
                txtbox_mobileno.AutoCompleteCustomSource = C;
            });
        });


        t.Start();
    }