/// <summary>
 /// 使变量名称为所传参数的cookie过期
 /// </summary>
 /// <param name="cookiename">cookie的变量的名称</param>
 public static void ClearCookie(string cookiename)
 {
     CookieHelper_HongRenHui.ClearUserCookie(MD5Tool.getMd5Hash(cookiename), domin);
 }