Host URL

                    string currentUrl = HttpContext.Current.Request.Url.ToString(); //In controller use System.web....
                    Uri uri = new Uri(currentUrl);
                    string domainURL = uri.Scheme + Uri.SchemeDelimiter + uri.Host + ":" + uri.Port;
                    string ReferrerURL = domainURL + "/admin/student/leadqualificationform/?personId=" + student.StudentId;
                    Uri ReferrerURI = new Uri(ReferrerURL);
                    string referrerText = "Source: " + student.ReferrerSource + Environment.NewLine + "Referrer: " + ReferrerURI;