Just a demo:
public void PopulateStudent(ID)
{
if (Convert.ToInt32(dr[0]["StudID"]) != 0)
{
RadioBtnList1.SelectedValue = dr[0]["StudentStatus"].ToString();
}
else
{
RadioBtnList1.Items[0].Selected = false;
RadioBtnList1.Items[1].Selected = false;
}
}