Dynamically changing ConnectionString in SQLDataSource in aspx.

I have 2 connection strings specified in my web.config. 

 How can I refer to the appropriate one depending on whether the app is live (production server) or test mode (say on localhost) from within the aspx file.

<connectionStrings>
 <add name="connStringLIVE" connectionString="..."/>
 <add name="connStringTEST" connectionString="..."/>
</connectionStrings>


<asp:SqlDataSource ID="sdsDataSource" DataSourceMode="DataSet" SelectCommandType="StoredProcedure"
        ConnectionString="<%$ ConnectionStrings:connStringTEST %>" SelectCommand="pStorProc"
        runat="server"></asp:SqlDataSource>


Thanks.
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