asp.net禁止页面刷新导致重复提交

网上找到的一个办法，也可以解决 用回车键代替提交按钮时，用户常按回车（非常快速的点回车）导致重复提交的情况： 
public class SubmitOncePage : System.Web.UI.Page
    {
        private string _strSessionKey;
        private string _hiddenfieldName;
        private string _strLastViewstate;
        public SubmitOncePage()
        {
            _hiddenfieldName = "__LastVIEWSTATE_SessionKey";
            _strSessionKey = System.Guid.NewGuid().ToString();
            _strLastViewstate = string.Empty;
        }
        public bool IsRefreshed
        {
            get
            {
                string str1 = GetSessinContent();
                _strLastViewstate = str1;
                string str2 = this.Session[GetSessinKey()] as string;
                bool flag1 = (str1 != null) && (str2 != null) && (str1 == str2);
  //str1就是Request.Form["__VIEWSTATE"];经过MD5加密
                return flag1;
            }
    &nb