listbox1.BeginUpdate(); // Stop the ListBox from drawing while items are added.
DataTable dt;
int IndexNum=listbox1.SelectedIndex;
dt=(DataTable)listbox1.DataSource;
DataRow custRow = dt.Rows[IndexNum];
custRow.BeginEdit();
custRow[0] = IndexNum;
custRow[1]="after modify";
custRow.EndEdit();
dt.AcceptChanges();
listbox1.EndUpdate();// End the update process and force a repaint of the ListBox.
listbox1.Update();
