Comment analyser la page URL JSON par page en utilisant C#

Question

Je suis nouveau sur C# et JSON. J'essaye d'analyser une URL de JSON qui a une limite de demande de 100 objets par page. Je ne suis pas en mesure de récupérer des pages au-delà de la première page avec 100 objets même s'il y a 2022 objets dans 21 pages.

Que manque-t-il dans mon code pour permettre l'analyse des 22 pages d'objets JSON?

Nous vous remercions de votre aide à l'avance!

Le nombre total d'objets est donnée par l'en-tête de réponse HTTP: X-Total-Count

public class VCUtils 
{ 
    public const string HeaderRateLimit = "X-Rate-Limit-Limit"; 
    public const string HeaderRateRemaining = "X-Rate-Limit-Remaining"; 
    public const string HeaderRateReset = "X-Rate-Limit-Reset"; 
    public const string HeaderCountTotal = "X-Total-Count"; 
} 

Ce qui suit est mon code de test.

protected void Page_Load(object sender, EventArgs e) 
{ 


    string baseURL = "https://api.veracross.com/vcdemo3/v2/students.json?page="; 
    int recordcount = 1; 
    int nextPage = 1; 
    int totalObjectCount = 0; 
    int defaultObjectsPerPage = 100; 
    int pageCount = 1000; 

    try 
    { 

     while (nextPage <= pageCount) //pageCount 
     { 
      string jsonData = ""; 

      var req = (HttpWebRequest)WebRequest.Create(baseURL + nextPage); 
      req.Credentials = new NetworkCredential(vcAPIUsername, vcAPIPassword); 
      req.PreAuthenticate = true; 
      HttpWebResponse response = req.GetResponse() as HttpWebResponse; 

      using (var reader = new System.IO.StreamReader(response.GetResponseStream())) { jsonData = reader.ReadToEnd(); } 
      // get total number of objects and calculate the page count 
      if (response.Headers[VCUtils.HeaderCountTotal] != null) 
      { 
       totalObjectCount = Convert.ToInt16(response.Headers[VCUtils.HeaderCountTotal]); 

       pageCount = (int)Math.Ceiling((double)totalObjectCount/(double)defaultObjectsPerPage); 
      } 


      VCStudents studentObj = new VCStudents(); 
      IList<VCStudents> validStudents; 

      // Call the JSON.NET deserializer helper method 
      validStudents = VCUtils.DeserializeToList<VCStudents>(jsonData); 



      foreach (var item in validStudents) 
      { 
       var studs = item.GetType().GetProperties(); 
       //** 

       int stkey = item.person_pk; //possibly legacy fields 
       string surname = item.last_name; 
       string first_name = item.first_name; 
       string pref_name = item.preferred_name; 
       string st_mobile = item.mobile_phone; 
       string st_email = item.email_1; 
       int gsis_id = item.person_pk; 
       string birthdate = item.birthday; 

       string gender = item.gender; 
       string lastupdatedate = item.update_date; 
       var fdkey = item.first_name; 


       Literal1.Text = Literal1.Text + recordcount + ") " + stkey + " " + surname + " " + first_name + " " + pref_name + " " + st_mobile + " " + st_email + " " + gsis_id + " " + birthdate + " " + roll_group + " " + gender + " " + fdkey + " " + lastupdatedate + "</br> "; 

       recordcount = recordcount + 1; 
      } 

      nextPage = nextPage + 1; 
     } 
    } 
    catch (Exception ex) 
    { 
     Console.WriteLine(ex.Message); 
    } 
    finally 
    { 

    } 
} 

Ce qui suit est la méthode JsonHelper référencé à partir, http://www.cshandler.com/2013/09/deserialize-list-of-json-objects-as.html#.WPguVUWGOJA

public static List<string> InvalidJsonElements; 
public static IList<T> DeserializeToList<T>(string jsonString) 
{ 
    InvalidJsonElements = null; 
    var array = JArray.Parse(jsonString); 
    IList<T> objectsList = new List<T>(); 

    foreach (var item in array) 
    { 
     try 
     { 
      // CorrectElements 
      objectsList.Add(item.ToObject<T>()); 
     } 
     catch (Exception ex) 
     { 
      InvalidJsonElements = InvalidJsonElements ?? new List<string>(); 
      InvalidJsonElements.Add(item.ToString()); 
     } 
    } 

    return objectsList; 
} 

Ce qui suit est la classe générée sur json2csharp.com

public class VCStudentRole 
{ 
    public string description { get; set; } 
} 

public class VCStudents 
{ 

    public const string studentsBasePath = "students"; 

    public int household_fk { get; set; } 
    public int person_pk { get; set; } 
    public string name_prefix { get; set; } 
    public string first_name { get; set; } 
    public string first_nick_name { get; set; } 
    public string preferred_name { get; set; } 
    public string middle_name { get; set; } 
    public string last_name { get; set; } 
    public string name_suffix { get; set; } 
    public string birthday { get; set; } 
    public string gender { get; set; } 
    public string email_1 { get; set; } 
    public bool display_email_1 { get; set; } 
    public string email_2 { get; set; } 
    public bool display_email_2 { get; set; } 
    public string home_phone { get; set; } 
    public bool display_home_phone { get; set; } 
    public string mobile_phone { get; set; } 
    public bool display_mobile_phone { get; set; } 
    public int advisor_fk { get; set; } 
    public string advisor_name { get; set; } 
    public int homeroom_teacher_fk { get; set; } 
    public string homeroom_teacher_name { get; set; } 
    public int homeroom { get; set; } 
    public List<VCStudentRole> roles { get; set; } 
    public string current_grade { get; set; } 
    public string grade_applying_for { get; set; } 
    public int year_applying_for { get; set; } 
    public bool resident_status_applying_for { get; set; } 
    public bool student_group_applying_for { get; set; } 
    public bool campus_applying_for { get; set; } 
    public string school_level { get; set; } 
    public string enrollment_status { get; set; } 
    public bool new_student { get; set; } 
    public int graduation_year { get; set; } 
    public string resident_status { get; set; } 
    public string campus { get; set; } 
    public string dorm { get; set; } 
    public string room_number { get; set; } 
    public int floor_number { get; set; } 
    public int bed_number { get; set; } 
    public string mailbox_number { get; set; } 
    public string student_group { get; set; } 
    public int parent_1_fk { get; set; } 
    public int parent_2_fk { get; set; } 
    public int parent_3_fk { get; set; } 
    public int parent_4_fk { get; set; } 
    public string username { get; set; } 
    public string update_date { get; set; } 

} 

Answer 1

Je doute que vous obtenez le nombre total précis ou non avec ce code:

totalObjectCount = Convert.ToInt16(response.Headers[VCUtils.HeaderCountTotal]); 

Vous pouvez essayer ceci:

totalObjectCount = Convert.ToInt32(response.Headers.Get(VCUtils.HeaderCountTotal)); 

Voir plus de détails à partir de MSDN: https://msdn.microsoft.com/en-us/library/system.net.webheadercollection(v=vs.110).aspx