function InitAutoCompl3() {

                                         
                                             $("#<%=txtAccountName.ClientID %>").autocomplete({
                                                 source: function (request, response) {
                                                     $.ajax({
                                                         url: '<%=ResolveUrl("~/DataWebService.asmx/GetAccounts2") %>',
                                                         data: "{ 'prefixText': '" + request.term + "'}",
                                                         dataType: "json",
                                                         type: "POST",
                                                         contentType: "application/json; charset=utf-8",
                                                         success: function (data) {

                                                             response($.map(data.d, function (item) {
                                                                 return {
                                                                     label: item.split('~')[1],
                                                                     val: item.split('~')[0]
                                                                 }
                                                             }))
                                                         },
                                                         error: function (response) {
                                                             alert(response.responseText);
                                                         },
                                                         failure: function (response) {
                                                             alert(response.responseText);
                                                         }
                                                     });
                                                 },
                                                 select: function (e, i) {
                                                     $("#<%=HFAcId2.ClientID %>").val(i.item.val);
                                                 },
                                                 minLength: 1
                                             });
                                     };

 $(document).ready(function () {
                                         var prm = Sys.WebForms.PageRequestManager.getInstance();
                                         prm.add_initializeRequest(InitializeRequest);
                                         prm.add_endRequest(EndRequest);

                                         // Place here the first init of the autocomplete
                                         InitAutoCompl3();  // in web user control
                                     });

                                     function InitializeRequest(sender, args) {
                                     }

                                     function EndRequest(sender, args) {
                                         // after update occur on UpdatePanel re-init the Autocomplete
                                         InitAutoCompl3();
                                     }

Required : SDK 13.0
Download link : https://developer.intuit.com/docs/0250_qb/0020_get_set_up/sdk_downloads
https://developer.intuit.com/Downloads/Restricted?filename=qbsdk130.exe

Sample Experimental Project :
https://onedrive.live.com/redir?resid=7D3B49FB4453E77A!1431&authkey=!AANhtiemRiGCDwk&ithint=file%2crar


Reference Guide: 

http://www.nullskull.com/a/1568/c-net-application-with-quickbooks-desktop-edition.aspx
https://mukarrammukhtar.wordpress.com/quickbooks-with-net/
http://qbblog.ccrsoftware.info/2010/03/quickbooks-add-on-programs-sdk/