Delete Selected Records Of Jqgrid In C#?

deleting selected records of jqgrid in asp.net c# for the following code

<script type="text/javascript">
var x = screen.width;
$(document).ready(function() {
jQuery("#table1").jqGrid({
url: 'griddata.aspx/DepartmentData?id=1',
datatype: 'json',
mtype: 'GET',
colNames: ['Department', 'Dept Code', 'Contact Person', 'Contact Phone','Contact Email'],
colModel: [
{ name: 'Department', index: 'Department', width: 55 },
{ name: 'Dept Code', index: 'Dept Code', width: 90 },
{ name: 'Contact Person', index: 'Contact Person', width: 40, align: 'center' },
{ name: 'Contact Phone', index: 'Contact Phone', width: 40, align: 'center' },
{ name: 'Contact Email', index: 'Conatct Email', width: 40, align: 'center' }],
pager: '#pager1',
rowNum: 15,
rowList: [10, 20, 30],
sortname: 'Department',
sortorder: "desc",
loadonce: true,
loadtext: "Loading....",
shrinkToFit: true,
multiselect: true,
emptyrecords: "No records to view",
width: x - 40,
height: 230,
rownumbers: true,
caption: 'DepartmentTable'
});
jQuery("#table1").jqGrid('navGrid', '#pager1', { edit: true, add: true, del: true });
});
</script>