jsonp解决跨域

 ajax请求：

$.ajax({
        type: "get",//必须使用get方式
        async: false,
        url: "http://www.lkhs.cn/ashx/LKHS_SJPush.ashx?dn=" + dn + "&AccessFrom=test",
        dataType: "jsonp",//jsonp
        jsonp: "jsonpCallback", //传递给请求处理程序或页面的，用以获得jsonp回调函数名的参数名(默认为:callback)
        jsonpCallback: "success_jsonpCallback", //自定义的jsonp回调函数名称，默认为jQuery自动生成的随机函数名
        success: function (json) {
        },
        error: function () {
        }
    });

function success_jsonpCallback(msg) {
    if (msg) {
        if (msg[0].count > 0) {
            $('#' + divId).append('<a href="http://www.lkhs.cn/hssj/' + dn + '_' + encodeURIComponent(ln).replace(/%/g, '$') + ly + '.html" target="_blank"><img id="img_bar" src="http://www.lkhs.cn/hs/images/sjts/sj_bar.gif" alt="汇商商机" width="525px" height="75px" /></a>')
            if (ly == '0')
                $('#' + divId).append('<a href="http://www.lkhs.cn/sjwap/' + dn + '_' + encodeURIComponent(ln).replace(/%/g, '$') + ly + '.html" target="_blank"><img id="img_bar" src="http://www.lkhs.cn/hs/images/sjts/sj_bar.gif" alt="汇商商机" width="525px" height="75px" /></a>')
        }
    }
}

后台：

if (AccessFrom == "test")
            {
                string CallJsMethod = Context.Request.Params["jsonpCallback"].ToString();//此处参数值为success_jsonpCallback
                try
                {
                    IList<TempletToCustomer> list = _service.GetListByDomainName(DomaninName);
                    if (list.Count > 0)
                    {
                        count = list.Count;
                    }
                    json.Append(CallJsMethod + "([{"count":" + count + "}])");//注意 返回数据格式

                }
                catch (Exception)
                {
                    json.Clear();
                }
        
            }

jsonp实现原理与实现过程：