How to place Dropdownlist1_selectedIndexChenged event in JSON.parse()

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ASP.NET

Javascript

function initialize() {

            var markers = JSON.parse('<%=ConvertDataTabletoString()%>');
            var mapOptions = {
                center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
                zoom: 5,
                mapTypeId: google.maps.MapTypeId.ROADMAP

            };

Please help me..how to place that event in JSON.Parse method..I already create "ConvertDataTableString()..but i want to change the location in dropdown list..for that i placed dropdown list..please say any one....