dropdownlist.selected value multiple values

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ASP.NET

Oracle

Hi i wonder if anyone can help me i have a dropdownlist which has 3 options.
the 1st 2 options in single value but the 3rd option is multiple values but when i run the sql script it returns no data. below is the sample of the dropdownlist

<asp:DropDownList ID="DropDownList1" runat="server">
            <asp:ListItem>--</asp:ListItem>
            <asp:ListItem>CO50</asp:ListItem>
            <asp:ListItem>COMP</asp:ListItem>
            <asp:ListItem Value="COMP,CO50">ALL</asp:ListItem>
        </asp:DropDownList>

and in my selectcommand i have the following

and MD IN :dropdownlistasp
and R.RCV_DATE between :datefrom and  :dateto

<SelectParameters>
                <asp:FormParameter FormField="dropdownlist1" 
                    Name="dropdownlistasp" />
                <asp:FormParameter FormField="textbox1" Name="datefrom" />
                <asp:FormParameter FormField="textbox2" Name="dateto" />
            </SelectParameters>

the 2 options which is single values return the correct data but the 3rd option with multiple values return nothing i have tried several values in the 3rd option and am not sure if it is possible

any assistance will be appreciated
thank you
Kallie