C# TextBox智能提示

private void Form1_Load(object sender, EventArgs e)
{
AutoCompleteStringCollection strings = new AutoCompleteStringCollection();
strings.Add("D1");//不区分大小写
strings.Add("D2");
strings.Add("Das");
strings.Add("E1");
strings.Add("Beijing");
strings.Add("EE-cims");
textBox1.AutoCompleteCustomSource = strings;
textBox1.AutoCompleteSource = AutoCompleteSource.CustomSource;
textBox1.AutoCompleteMode = AutoCompleteMode.Suggest;
}