How Can I Get This Event When I Select Item In Radiobuttonlist

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C#

ASP.NET

datalist

RadioButton

i have nested datalist ,

<asp:DataList ID="datalist_iq" runat="server" DataKeyField="id" BorderColor="Red">
                               <ItemTemplate>

                                   <table border="1">
                                       <tr>
                                           <td>
                                               <asp:Label ID="label_question_head" runat="server" Style="word-wrap: break-word" Width="310px" Height="91px" Font-Bold="true" ForeColor="Maroon">
                                                                   <%#Eval("q_head") %>

                                               </asp:Label>


                                           </td>
                                       </tr>

                                       <tr>

                                           <td>
                                               <asp:RadioButtonList ID="RadioButton1" OnSelectedIndexChanged="RadioButton1_SelectedIndexChanged"   DataTextField="a_head" DataValueField="result" runat="server" Visible="true" >


                                               </asp:RadioButtonList>

                                           </td>
                                       </tr>
                                   </table>


                              </ItemTemplate>
                         </asp:DataList>

i want to get DataKeyField when i select item in radiobuttonlist
how can i get this event


i can retrive the radiobuttonlist by this code

foreach (DataListItem dli in datalist_iq.Items)
{
     rblfilteritem = (RadioButtonList)dli.FindControl("RadioButton1");
    a_content = q_object.retrive_a((int)datalist_iq.DataKeys[dli.ItemIndex]);
    rblfilteritem.DataSource = a_content;
    rblfilteritem.DataBind();



}

but i want to access the event when i select one radiobutton