Pass two parameters to ajax cascading dropdownlist

Hello everyone, I need to pass two parameters to ajax cascading dropdownlist, how could I do that? Here is my code:

<div class="row"><cc1:MyDropdownList ID="ddlLocation" runat="server"></cc1:MyDropdownList><ajaxToolkit:CascadingDropDown ID="cdlLocation" TargetControlID="ddlLocation" PromptText="-- Select a location --"
                PromptValue="0" ServicePath="~/CascadingDdl.asmx" ServiceMethod="GetLocation" runat="server"
                Category="location_id" LoadingText="-- Select a location --" /></div><div class="row"><cc1:MyDropdownList ID="ddlCategory" runat="server"></cc1:MyDropdownList><ajaxToolkit:CascadingDropDown ID="cdlCategory" TargetControlID="ddlCategory" PromptText="-- Select a category --"
            PromptValue="0" ServicePath="~/CascadingDdl.asmx" ServiceMethod="GetCategory" runat="server"
            Category="parent_id" ParentControlID="ddlLocation" LoadingText="-- Select a category --" /></div><div class="row"><cc1:MyDropdownList ID="ddlProduct" runat="server"></cc1:MyDropdownList><ajaxToolkit:CascadingDropDown ID="cdlProduct" TargetControlID="ddlProduct" PromptText="-- Select a product --"
                        PromptValue="0" ServicePath="~/CascadingDdl.asmx" ServiceMethod="GetProduct" runat="server"
                        Category="current_location_id" ParentControlID="ddlCategory" LoadingText="-- Select a product --" /></div>

So in the final dropdownlist, I need two parameters, location_id from the location dropdownlist and category_id from the category dropdownlist. 

Thanks for your help.