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;  }