public partial class Form4 : Form
{
  private Bitmap myBitmap;
  public Form4()
  {
   InitializeComponent();
   DataTable dt = new DataTable();
   DataColumn dc1 = new DataColumn("Name", typeof(System.String));
   DataColumn dc2 = new DataColumn("Age", typeof(System.String));
   dt.Columns.Add(dc1);
   dt.Columns.Add(dc2);
   for (int i = 0; i < 20; i++)
   {
    DataRow row = dt.NewRow();
    row["Name"] = i.ToString();
    row["Age"] = i.ToString();
    dt.Rows.Add(row);
   }
   comboBox1.DataSource = dt;
  }
  private void comboBox1_Format(object sender, ListControlConvertEventArgs e)
  {
   DataRowView myDataRowView = (DataRowView)(e.ListItem);
   e.Value = string.Format("{0}-{1}-{2}", myDataRowView["Name"], myDataRowView["Name"], myDataRowView["Name"]);
  }
}