C# reading JSON from web API

Question

I am trying to read data from this API API Wykazu podatników VAT

Thru HttpWebRequest it's working:

 HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://wl-test.mf.gov.pl:9091/wykaz-podatnikow/api/search/nips/3245174504?date=2019年09月27日");
 try
 {
 WebResponse response = request.GetResponse();
 using (Stream responseStream = response.GetResponseStream())
 {
 StreamReader reader = new StreamReader(responseStream, System.Text.Encoding.UTF8);
 Console.WriteLine(reader.ReadToEnd());
 }
 }
 catch (WebException ex)
 {
 WebResponse errorResponse = ex.Response;
 using (Stream responseStream = errorResponse.GetResponseStream())
 {
 StreamReader reader = new StreamReader(responseStream, System.Text.Encoding.GetEncoding("utf-8"));
 String errorText = reader.ReadToEnd();
 // log errorText
 }
 throw;
 }

But when I try it thru WebClient:

 var client = new WebClient();
 client.Headers.Add("nips", "3245174504");
 client.Headers.Add("date", "2019-09-27");
 var response = client.DownloadString("https://wl-test.mf.gov.pl:9091/wykaz-podatnikow/api/search/nips/");
 Console.WriteLine(response.ToString());

I got this error message:

Unhandled Exception: System.Net.WebException: An exception occurred during a WebClient request. ---> System.ArgumentException: The 'date' header must be modified using the appropriate property or method. Parameter name: name at System.Net.WebHeaderCollection.ThrowOnRestrictedHeader(String headerName) at System.Net.WebHeaderCollection.Add(String name, String value) at System.Net.HttpWebRequest.set_Headers(WebHeaderCollection value) at System.Net.WebClient.CopyHeadersTo(WebRequest request) at System.Net.WebClient.GetWebRequest(Uri address) at System.Net.WebClient.DownloadDataInternal(Uri address, WebRequest& request) --- End of inner exception stack trace --- at System.Net.WebClient.DownloadDataInternal(Uri address, WebRequest& request) at System.Net.WebClient.DownloadString(Uri address) at System.Net.WebClient.DownloadString(String address)

How should I format the second Date parameter?

• M. A. Cordeiro: Are you sure you have to add these the parameters in the header? Once it is a "get" request it is supposed to be on the url like in the first example.
• Ivo Oostwegel: If you want to change the date parameter check this link: link

Answer 1

I would recommend using the newer HTTPClient as it is specifically created for API calls -

 using (var x = new HttpClient())
 {
 var y = x.GetAsync("https://wl-test.mf.gov.pl:9091/wykaz-podatnikow/api/search/nips/3245174504?date=2019年09月27日").Result;
 var json = y.Content.ReadAsStringAsync().Result;
 }

Just to add, please don't use .Result, instead use the async/await operators.

• Fildor: But not like this ! See contrivedexample.com/2017/07/01/… or aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong or josefottosson.se/…
• R Jain: yes sorry edited that just did that for sample purpose only
• Jeya Kumar: Hi, what is that "date=2019年09月27日" is it a registered date of that number ?

Answer 2

Are you mistaking request headers with Query Parameters? if so you might want the following instead:

https://wl-test.mf.gov.pl:9091/wykaz-podatnikow/api/search?nips=3245174504&date=2019年09月27日