How to get "Host:" header from HttpContext (asp.net)

string requestedDomain = HttpContext.Current.Request.ServerVariables["HTTP_HOST"];
string requestScheme = HttpContext.Current.Request.Url.Scheme;
string requestQueryString = HttpContext.Current.Request.ServerVariables["QUERY_STRING"];
string requestUrl = HttpContext.Current.Request.ServerVariables["URL"];

HttpContext.Current.Request.Url.Host