private static string BuildFinalUrl(this HttpClient httpClient, string url, QueryString queryString = null)
{
var finalUrl = UrlUtility.Combine(httpClient.BaseAddress.OriginalString, url);
if (queryString == null)
{
return(finalUrl.ToString());
}
finalUrl = UrlUtility.AppendQueryString(finalUrl, queryString.ToString());
return(finalUrl);
}