asp.net下拉框无限极分类（递归）（项目是nicpetshop代码生成器生成的）

public partial class _Default : System.Web.UI.Page
{
    List<ModelsInfo> list = Models.GetItems();  //获取该表中全部信息
    protected void Page_Load(object sender, EventArgs e)
    {

        if (!IsPostBack)
        {
            loadData();    //加载数据
        }
    }
    /// <summary>
    /// 加载数据
    /// level深度
    /// </summary>
    public void loadData()
    {
        DropDownList1.Items.Clear();  //清除
        DropDownList1.Items.Add(new ListItem("全部","0"));
        string str = "+";
        //根据条件对信息进行筛选
        List<ModelsInfo> temp = list.FindAll(delegate(ModelsInfo m) {
            return m.Level == 1;
        });
        //循环所有分类级
        foreach(ModelsInfo info in temp)
        {
            DropDownList1.Items.Add(new ListItem(str+info.Model_name,info.Id.ToString()));
            loadSunData(info,ref str);
        }
        DropDownList1.DataBind();
    }
    /// <summary>
    /// 递归
    /// </summary>
    public void loadSunData(ModelsInfo info1,ref string strs)
    {
        List<ModelsInfo> list1 = list.FindAll(delegate(ModelsInfo m1) {
            return m1.Sun_id == info1.Id;
        });
        foreach(ModelsInfo temp1 in list1)
        {
            if(temp1.Sun_id==info1.Id){
                strs = "+" + strs;
                DropDownList1.Items.Add(new ListItem(strs+temp1.Model_name, temp1.Id.ToString()));
                loadSunData(temp1,ref strs);
            }
            strs = "+";
        }
    }
   
}