To get querystring variable of Parent Page URL from iframe

To get Parent page url from iframe:

string url = HttpContext.Current.Request.UrlReferrer.OriginalString.ToString();

To get QueryString from url of parent page, use:

string query = HttpContext.Current.Request.UrlReferrer.Query;

To get values of parameters from url use:

string[] queryStringParaArray = HttpContext.Current.Request.UrlReferrer.Query.Substring(1).Split('=');

     if (queryStringParaArray.Length > 0)

     {

        foreach (var para in queryStringParaArray)

             if (para == "EventId")

                 int eventId = Convert.ToInt32(queryStringParaArray[1]);

     }