AutoComplete ComboBox Control From Database

C#

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Autocomplete_controls_csharp
{
    public partial class Form1 : Form
    {
        private string connStr = @"data source=.\sqlexpress;database=northwind;integrated security=true";
        DataTable dt;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Configure_ComboBox();
        }
        void Configure_ComboBox()
        {
            this.Connect();
            if (dt == null)
            {
                MessageBox.Show("Error in Quering");
                return;
            }
            IList<string> lstFirst = new List<string>();
            IList<string> lstLast = new List<string>();
            foreach (DataRow row in dt.Rows)
            {                
                lstFirst.Add(row.Field<string>("firstname"));
                lstLast.Add(row.Field<string>("lastname"));
            }                                        
            this.comboBoxFirstName.Items.AddRange(lstFirst.ToArray<string>());
            this.comboBoxFirstName.AutoCompleteMode = AutoCompleteMode.Suggest;
            this.comboBoxFirstName.AutoCompleteSource = AutoCompleteSource.ListItems;

            this.comboBoxLastName.Items.AddRange(lstLast.ToArray<string>());
            this.comboBoxLastName.AutoCompleteMode = AutoCompleteMode.Suggest;
            this.comboBoxLastName.AutoCompleteSource = AutoCompleteSource.ListItems;
        
        }
        void Connect()
        {
            SqlConnection conn = new SqlConnection(this.connStr);
            try
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(@"select firstname,lastname from employees", conn);
                SqlDataAdapter ada = new SqlDataAdapter(cmd);
                dt = new DataTable();
                ada.Fill(dt);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error:" + ex.Message.ToString());
            }
            finally { conn.Close(); }
        }
    }
}

Visual Basic

Imports System.Data
Imports System.Data.SqlClient
Public Class Form1
    Private connStr As String = "data source=.\sqlexpress;database=northwind;integrated security=true"
    Dim dt As DataTable
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Configure_ComboBox()
    End Sub
    Sub Configure_ComboBox()
        Me.Connect()
        If dt Is Nothing Then
            MessageBox.Show("Error in Quering")
            Exit Sub
        End If
        Dim lstFirst As IList(Of String) = New List(Of String)
        Dim lstLast As IList(Of String) = New List(Of String)
        For Each _row As DataRow In dt.Rows
            lstFirst.Add(_row("firstname"))
            lstLast.Add(_row("lastname"))
        Next
        Me.ComboBoxFirstName.Items.AddRange(lstFirst.ToArray)
        Me.ComboBoxFirstName.AutoCompleteMode = AutoCompleteMode.Suggest
        Me.ComboBoxFirstName.AutoCompleteSource = AutoCompleteSource.ListItems
        Me.ComboBoxLastName.Items.AddRange(lstLast.ToArray)
        Me.ComboBoxLastName.AutoCompleteMode = AutoCompleteMode.Suggest
        Me.ComboBoxLastName.AutoCompleteSource = AutoCompleteSource.ListItems
    End Sub
    Sub Connect()
        Dim conn As New SqlConnection(connStr)
        Try
            conn.Open()
            Dim cmd As New SqlCommand("select firstname,lastname from employees", conn)
            Dim ada As New SqlDataAdapter(cmd)
            dt = New DataTable
            ada.Fill(dt)
        Catch ex As Exception
            MessageBox.Show("Error:" & ex.ToString)
        Finally
            conn.Close()
        End Try
    End Sub
End Class