ext 表单的提交成功后，无法返回？

我的保存按钮
buttons:[{
text:"保存信息(S)",
id:"save",
minWidth:70,
handler:function()
{
if(AddPublishForm.getForm().isValid())
                            {
                                //弹出效果
                                Ext.MessageBox.show
                                (
                                    {
                                        msg: '正在保存，请稍等...',
            progressText: 'Saving...',
            width:300,
            wait:false,
            waitConfig: {interval:2000},
            icon:'download',
            animEl: 'saving'
                                    }
                                );
                                setTimeout(function(){}, 1000);
                                AddPublishForm.form.submit({
                                    url:"URL/jydbh/savejydinfo.aspx",
                                    method:"POST",
                                    success:function(form,action)
                                    {
                                        //成功后
                                        var flag=action.result.success;
                                        if(flag=="true")
                                        {
                                            Ext.MessageBox.alert("提示","添加新的交易单成功!");
                                            PublishInfoStore.reload();
                                            AddPublishwin.hide();
                                        }                                           
                                    },
                                    failure:function(form,action)
                                    {
                                        PublishInfoStore.reload();
                                        Ext.MessageBox.alert("提示!","新交易单添加失败!");
                                    }
                                });
                           }
}
}savejydinfo.aspx代码        SQLHelper sqlHelp = new SQLHelper();
        string result = "";
        string jydbh = Request.Form["jydbh"];
        string jydzt = Request.Form["jydzt"];
        string cmd1 = "update jydxx set jydzt='" + jydzt + "' where jydbh='" + jydbh + "'";
        sqlHelp.RunSQL(cmd1);        if (result)
        {
            Context.Response.Write("{success:true;errors:{}}");
        }
        else
        {
            Context.Response.Write("{success:false,errors:{info:'插入失败'}}");
        }        Response.Write(result);
       ｝前台怎么老是无法提示添加成功呢？但是后台数据库确实是添加进去了啊？我看了错误信息 好像是返回的json格式错误了
不知道要如何返回给前台 提示添加成功呢？