Please help to implement Dropdown list in my project

Question

here is my aspx code
 
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"> <asp:ListItem>Mark as </asp:ListItem> <asp:ListItem>Mark as Read</asp:ListItem> <asp:ListItem>Mark as Unread</asp:ListItem>   </asp:DropDownList> 

when i click on dropdown list
i want only two option shuld drop as Mark as Read and Mark as UnRead
 
but mark as option also getting drop
 
i want it to be intact @ dropdown text
even when user select Mark as Read then also it shuld be der @ dropdown text
 
Please help
Many Thanks..