How to communicate to database using AJAX

I am trying to communicate to database from JavaScript using AJAX.

I have followed one article A beginner’s guide for consuming a WCF service in JavaScript using ASP.NET AJAX to understand about this functionality. I have done everything like exactly shown in the article. But, I couldn't understand how to set up the communication from JavaScript file.

Please note that as per my project requirement I can use only the second techniq开发者_如何转开发ue explained in the article: Using a Service Interface Defined in the Class Library.

Can anybody please suggest me how to do this?

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Follow these steps 1) Creat a WCF service in your application. 2) Then add reference to your WCF Service. 3) Then add wcf service to the script manager control of your page 4) Now you can access the wcf service on your page.

Step by Step tutorial using VB.NET http://v4.ajaxtutorials.com/tutorials/javascript/expose-wcf-service-to-javascript-in-asp-net-4-0-vb/

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I used the following JavaScript code to get data from the database over AJAX:

$(function () {
    var search = $("#<%=txtAccountNo.ClientID%>");
    search.watermark('Enter Account No');
    search.autocomplete({
        source: function (request, response) {
        $.ajax({
            url: '<%=ResolveUrl("~/") %>AutoCompleteService.asmx/GetAccountNo',
            data: "{'prefixText':'" + search.val() + "','count':'10','contextKey':''}",
            dataType: "json",
            type: "POST",
            contentType: "application/json; charset=utf-8",
            dataFilter: function (data) { return data; },
            success: function (data) {
                if (data.d != null) {
                    response($.map(data.d, function (item) {
                        return {
                            value: item
                        }
                    }))
                }
             },
            error: function (XMLHttpRequest, textStatus, error) {
                //alert(textStatus);
            }
        });
        },
     minLength: 1
    });
});