Handle textbox and listbox combination

Hi
   Your problem has solved, see the following code or find in attachment.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace testcombo
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void textBox1_TextChanged(object sender, EventArgs e)
{
if (textBox1.Text != "")
{
}
else
{
return;
}
listBox2.Items.Clear();
for (int i = 0; i < listBox1.Items.Count; i++)
{
if (listBox1.Items[i].ToString().Contains(textBox1.Text))
{
listBox2.Visible = true;
if (!listBox2.Items.Contains(textBox1.Text))
{
listBox2.Items.Add(listBox1.Items[i]);
}
}
}
}

private const int WM_VSCROLL = 0x115;

[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, UIntPtr wParam, IntPtr lParam);

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
switch (e.KeyCode)
{
case Keys.Up:
if (listBox2.Items.Count > 1)
{
if (listBox2.SelectedIndex > 0)
listBox2.SelectedIndex = listBox2.SelectedIndex - 1;
}
else if (listBox2.Items.Count == 1)
{
listBox2.SelectedIndex = 0;
}
break;
case Keys.Down:
if (listBox2.Items.Count > 1)
{
if (listBox2.SelectedIndex != listBox2.Items.Count - 1)
listBox2.SelectedIndex = listBox2.SelectedIndex + 1;
}
else if (listBox2.Items.Count == 1)
{
listBox2.SelectedIndex = 0;
}
break;
case Keys.Enter:
if (listBox2.SelectedIndex != -1)
{
textBox1.Text = listBox2.Text;
listBox2.Visible = false;
}
break;
}
}
}
}