Pass two parameters to ajax cascading dropdownlist

Hello everyone, I asked this question in ajax forum but was quiet. So I am searching for help in this forum instead. 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> <ajax ...