Ext.data.HttpProxy的问题，关于grid加载acion返回数据??

前台extjs 代码
JScript code

var ds = new Ext.data.Store({
    proxy: new Ext.data.HttpProxy({ url: "../../URL/ddgl/GetBaohuo.aspx" }),
    reader: new Ext.data.JsonReader({
}, [
        { name: 'hwmc', mapping: 0 },
        { name: 'js', mapping: 1 },
        { name: 'ztj', mapping: 2},
        { name: 'zzl', mapping: 3 },
        { name: 'beizu', mapping: 4 }

    ]),
pruneModifiedRecords: true,
sortInfo: { field: "hwmc", direction: "ASC" }
});

后台 c# 
C# code

string FNumber = Request.Params["FNumber"];
        string cmd1 = "";
        if (FNumber == "")
        {
            cmd1 = "select id,bhid,hwmc,js,ztj,zzl,beizu from baohuodetails";     
        }
        else
        {
            cmd1 = "select id,bhid,hwmc,js,ztj,zzl,beizu from baohuodetails  where bhid='" + FNumber + "'";
        }
        
        DataSet ds = sqlHelp.GetDataSet(cmd1);
        int count = ds.Tables[0].Rows.Count;

        for (int i = 0; i < count;i++ )
        {
            result = "[['" + ds.Tables[0].Rows[i]["hwmc"].ToString().Trim() + "','" + ds.Tables[0].Rows[i]["js"].ToString() + "','" + ds.Tables[0].Rows[i]["ztj"].ToString() + "','" + ds.Tables[0].Rows[i]["zzl"].ToString() +
                     "','" + ds.Tables[0].Rows[i]["beizu"].ToString() + "' " + "]" +
                     "]";
        }

如果有多行数据的话 只能输出最后一行?
看了一下好像要输入[[],[],[],....] 这种格式才行!!
要怎么组织呢?

网上搜Ext grid的store格式 和jsonStore的用法