ExtJs Combobox绑值问题
asp.net mvc+extJs3.0

1.后台返回的是Json
public ActionResult GetBrandMsg()
{
//获取所有品牌
List<Brand> brands = BrandManager.GetAllBrand();
//返回的json我打印了看了下，是这样的：
[{"Id":1,"BrandName":"雪弗兰"},{"Id":2,"BrandName":"别克"},{"Id":3,"BrandName":"宝马"}]
return this.Json(brands, JsonRequestBehavior.AllowGet);
}

2.前台：
Ext.onReady(function() {
var myStore = new Ext.data.JsonStore({
autoLoad: true,
proxy: new Ext.data.HttpProxy({
url: "Car/GetBrandMsg"
}),
fields: ["Id", "BrandName"]
});
------------------------------------------------------
xtype: "combo",
name: "brands",
model: "remote",
store: myStore,
selectOnFocus: true,
loadingText: "正在加载数据",
triggerAction: "all",
displayField: "BrandName",
valueField: "Id",
fieldLabel: "品牌",
emptyText: "--请选择品牌--",
width: 200
------------------------------------------------------

问题：combobox总是没有值显示，请高手帮忙看下是什么原因

[解决办法]
你的数据格式有错
{"items":[{"Id":1,"BrandName":"雪弗兰"},{"Id":2,"BrandName":"别克"},{"Id":3,"BrandName":"宝马"}]}

[解决办法]
autoLoad:false
[解决办法]
确定你的store到后台去请求了数据?