asp.net中，给RadioButtonList动态赋值？

<%
RadioButtonList1.Items.Add(new ListItem("100~90分", "O"));
RadioButtonList1.Items.Add(new ListItem("90~80分", "V"));
RadioButtonList1.Items.Add(new ListItem("80~70", "G"));
RadioButtonList1.Items.Add(new ListItem("80~70", "I"));
RadioButtonList1.Items.Add(new ListItem("80~70", "U"));

string Score = "V";
ListItem item = RadioButtonList1.Items.Cast().Where(o => o.Value == Score).SingleOrDefault();
int index = RadioButtonList1.Items.IndexOf(item);

if (item!=null)
{
RadioButtonList1.SelectedIndex = index;
}
else
{
RadioButtonList1.Items.Add(new ListItem("数据库添加",Score));
}

%>

数据库中Score的值不要为空，设为 -1

单选按钮

判断啊