页面中保存变量的有关问题

页面中保存变量的问题
方法一:
private   int   FlowID;//窗体类变量
private   void   Page_Load(object   sender,   System.EventArgs   e)
{
FlowID   =   Request.QueryString[ "FlowID "]!=null?Int32.Parse//(Request.QueryString[ "FlowID "].ToString()):0;
}
方法二
public　void   aa(){
ViewState[ "DocID "]   =   Convert.ToInt32(Request.QueryString[ "DocID "]);
}
请问哪个方式好？请说明下理由？谢谢

------解决方案--------------------------------------------------------
通常情况下应该选用方法二，另外方法二可以改成属性，调用起来就方便了
public　int aa
{
get
{
if (ViewState[ "DocID "] != null)
{
return Convert.ToInt32(ViewState[ "DocID "]);
}
else
{
return -1;
}
}
set
{
ViewState[ "DocID "] = value;
}
}