extjs用ajax获取json数据不能转换成Store
前台代码:

Ext.onReady(function () {

            var store = new Ext.data.Store({

                fields: [{ name: 'user_id' }, { name: 'user_name' }, { name: 'ssyj', type: "float"}],

                reader: new Ext.data.JsonReader({ totalProperty: "results", root: 'data' })

//                listeners: {

//                    load: function () {

//                        alert(store.getCount());

//                    }

//                }

            });

            var requestConfig = {

                url: '/WebService/test/tb_data.ashx', //请求的服务器地址

                params: { userName: 'tom', password: '123' }, //请求参数

                customer: '自定义属性', //附加属性

                callback: function (options, success, response) {//回调函数

                    alert(response.responseText);

                    var forminfo = Ext.decode(response.responseText);

                    store.loadData(Ext.JSON.decode(response.responseText,true));

                    alert(store.getCount());

                }

            }

            Ext.Ajax.request(requestConfig); //发送请求

返回的json数据字符串:
{"results":3,"data":[
{"user_name":"郑正英","user_id":"10","ssyj":"39569.0100"},
{"user_name":"王雪梅","user_id":"11","ssyj":"557619.9900"},
{"user_name":"张丹青","user_id":"12","ssyj":"116000.0000"},
{"user_name":"张海东","user_id":"13","ssyj":"1412742.9900"}]}

后台代码:

public void ProcessRequest(HttpContext context)

        {

            context.Request.ContentEncoding = Encoding.GetEncoding("UTF-8");