Ajax static method in master page

I have below coding to show a slideshow in MasterPage

<asp:Panel ID="Panel5" runat="server" Width="700px" Height="150px"><asp:Image runat="server" ID="img" Width="700px" Height="150px" /><asp:SlideShowExtender ID="SlideShowExtender5" runat="server" SlideShowServiceMethod="GetSlides" TargetControlID="img" UseContextKey="True"></asp:SlideShowExtender></asp:Panel>

To where I can add this GetSlides() static method in master page? Because it gives an runtime error always method is not available.