Help - C # how to update comboBox? autocomplete type

Firstly I'm developing a system in C # and using Sql Server as a database.

I would like to perform the following task: When something is typed in the comboBox I update myself, through a search in the database, example:

I type A in the comboBox and loads it with the return of the select.

Another example: Same as google search, american, extra, and so on. Style an autocomplete, it is necessary to use the comboBox, because in it I have to bring the name on the display and the code in the value of the comboBox.

Style an autocomplete, but I need it to be a comboBox because in it I bring a code together.

I've programmed it as follows:

exe:

comboBox.DataSource = dataTable;
comboBox.DisplayMember = "Nome";
comboBox.ValueMember = "codigo;

Inside the TextChanged of the comboBox.

The select is right and the dataTable is correct, but I am having the following problem the comboBox takes the first line that returns and does not leave I continue typing, nor changes to low register (OBS: Returns more than one line) nor at least it shows the list, it simply "hangs" on the first line.

I do not know if it has to configure some property of the comboBox or perform in a specific event ...

Firstly I had done an autocomplete in a textBox, it works but I can not pick the code the option is selected for.

And I did not want to load the comboBox with all the records. So there's something heavy.

More specifically I'm doing a sales-related form, and I'm researching the client that way. I do not know if there's any way.

I'm grateful for any suggestions right now.

Update -

comboBox textChanged chord

    private void cmbNome_Cliente_TextChanged(object sender, EventArgs e)
    {
        Cliente cliente = new Cliente();
        cliente.Nome = cmbNome_Cliente.Text;
        cliente.Razao_social = cmbNome_Cliente.Text;


        cmbNome_Cliente.DataSource = cliente.CarregaClienteNome(); "Isso retorna um dataTable"
        cmbNome_Cliente.DisplayMember = "Nome - Razao Social";
        cmbNome_Cliente.ValueMember = "Código";
    }

// Find Client for the ComboBox by the name ## updated

    public DataTable CarregaClienteNome()
    {
        SqlDataAdapter da = new SqlDataAdapter();
        DataTable dt = new DataTable();

        try
        {
            conn.Open();
            cmd.Connection = conn;

            cmd.CommandText = "select top(5) cli.cod_cliente as Código, ";
            cmd.CommandText += "(case when pes.cod_tipo_pessoa = 1 then Nome else Razao_Social end) as 'Nome - Razao Social' ";
            cmd.CommandText += "from tab_Pessoa pes ";
            cmd.CommandText += "inner join tab_Cliente cli on pes.cod_pessoa = cli.cod_pessoa ";
            cmd.CommandText += "where pes.nome like '" + Nome + "%' or pes.razao_social like '" + Razao_social + "%'";
            cmd.CommandText += " order by 'Nome - Razao Social'";

            da.SelectCommand = cmd;
            da.Fill(dt);
            cmd.ExecuteNonQuery();
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message);
        }
        finally
        {
            conn.Close();
        }

        return dt;
    }

// Autocomplete - test that I did with autocomplete in a textBox, it is working. But I can not get the code

private void txtTeste_TextChanged(object sender, EventArgs e)
    {
        Cliente cliente = new Cliente();

        cliente.Nome = txtTeste.Text;
        cliente.Razao_social = txtTeste.Text;

        DataTable dt = new DataTable();

        var source = new AutoCompleteStringCollection();

        dt =cliente.CarregaClienteNome();

        for (int i = 0; i < dt.Rows.Count; i++)
        {
            source.Add(dt.Rows[i][1].ToString());
        }


        txtTeste.AutoCompleteCustomSource = source;            

    }