API請求在應用程序中失敗，但在瀏覽器中工作

Question

所以我想從我的Android應用程序中使用Xamarin的API（我無法控制）獲取一些信息。

它的工作原理！如果我將生成的鏈接粘貼到Chrome中，或者使用Chrome擴展郵件管理器，但我無法在我的應用程序中正常工作，我會得到我想要的信息。

應用程序處於poc狀態，因此一切都在主它實現了ILocationListener並請求GPS每3秒更新，但在這裏活動是代碼的有趣的部分：

public void OnLocationChanged(Location location) { 

     var lat = location.Latitude; 
     var lon = location.Longitude; 

     _lat.Text = "lat: " + lat; 
     _lon.Text = "lon: " + lon; 

     // get the vegReference (roadReference) based on the lat & lon 
     var url = "https://www.vegvesen.no/nvdb/api/vegreferanse/koordinat?lon=" + lon.ToString("") + "&lat=" + lat.ToString("") + "&geometri=WGS84"; 

     // ex: https://www.vegvesen.no/nvdb/api/vegreferanse/koordinat?lon=10.399547&lat=63.354658&geometri=WGS84 

     var json = new JSONObject(Get(url)); 

     Log.Debug("url", url); 
     Log.Debug("json", json.ToString()); 

     if (json.GetString("kommuneNr") == "0") return; // bug in API? 

     var kommuneNr = json.GetString("kommuneNr"); 

     var vegReferanse = json.GetString("visningsNavn"); 

     // get the object id 105 (speed limit) on set vegReference 
     // API dok: https://www.vegvesen.no/nvdb/apidokumentasjon/#/get/vegobjekter 
     var url2 = "https://www.vegvesen.no/nvdb/api/v2/vegobjekter/105?vegreferanse=" + vegReferanse.Replace(" ", "") + "&inkluder=lokasjon&segmentering=false"; 

     // ex. https://www.vegvesen.no/nvdb/api/v2/vegobjekter/105?vegreferanse=PV3133HP1m73&inkluder=lokasjon&segmentering=false 

     // this (url2) is the one that fails 

     Log.Debug("url2", url2); 

     var json2 = new JSONObject(Get(url2)); 

     Log.Debug("json2", json2.ToString()); 

     // get the speed limit with the heighest id (this should be the latest one (FYI: speedlimits have changed over the years, all speed limits are in the database for historical reasons(?))) 

     var objs = json2.GetJSONArray("vegObjekter"); 

     var list = new List<JSONObject>(); 


     // getting a list of possible objects based on the kommuneNr (because for some f*ced up reason the result returns objects in other kommunes aswell...) 
     for (int i = 0; i < objs.Length() - 1; i++) 
     { 
      if (objs.GetJSONObject(i).GetJSONObject("lokasjon").GetJSONArray("kommuner").GetString(0) == kommuneNr) 
       list.Add(objs.GetJSONObject(i)); 
     } 

     if (list.Count == 0) return; 

     var url3 = list[list.Count - 1].GetString("href"); 

     // ex. https://www.vegvesen.no/nvdb/api/v2/vegobjekter/105/276790644 

     Log.Debug("url3", url3); 

     var json3 = new JSONObject(Get(url3)); 

     Log.Debug("json3", json3.ToString()); 

     // set the speed-limit to the textview. 

     var res = json3.GetJSONArray("egenskaper").GetJSONObject(0).GetString("verdi"); 
     _tvSl.Text = res + " km/t"; 

    } 

而且Get - 方法beeing稱爲OnLocationChanged內，基本上只獲得響應作爲一個字符串：

private string Get(string url) 
     { 
      var request = WebRequest.Create(url); 

      var sb = new StringBuilder(); 
      var response = (HttpWebResponse)request.GetResponse(); 

      using (var sr = new StreamReader(response.GetResponseStream())) 
      { 
       sb.Append(sr.ReadToEnd()); 
      } 
      return sb.ToString(); 
     } 

從URL2-請求的響應是這樣的：

System.Net.WebException: The remote server returned an error: (500) Internal Server Error. 

我的問題是;爲什麼鏈接（ref url2）在瀏覽器中運行，而不是在應用程序中運行。

任何幫助或指針在這個問題將不勝感激！ 另請參見：鏈接到GitHub上的項目：https://github.com/Nemeas/alfaOmega

Answer 1

好吧，經過大量的試驗和錯誤，我發現問題是有一個丟失的標題; accept: application/json（看起來這只是這個api（？）的v2的情況）。我嘗試使用WebRequest添加標題，但每當我到達添加標題的行時都會收到錯誤。然而，還有另一個WebRequest，名爲HttpWebRequest，其中accept作爲屬性而不是通過列表公開，並且這是有效的。所以我必須做的唯一的改變是在Get方法，結果是這樣的：

public static string Get(string url) 
    { 
     // casting request to HttpWebRequest to expose Accept as a property 
     var request = (HttpWebRequest)WebRequest.Create(url); 
     request.Accept = "application/json"; 

     var sb = new StringBuilder(); 

     // getting the response 
     var response = (HttpWebResponse)request.GetResponse(); 

     using (var sr = new StreamReader(response.GetResponseStream())) 
     { 
      sb.Append(sr.ReadToEnd()); 
     } 

     var res = sb.ToString(); 

     // returning the response as a string 
     return res; 
    }