Looping does not work in JSON serialization using Web Api Controller ASP.NET MVC

Question

I am trying to Deserilize json data from wikipedia api. I want to get only the Image information and then serilize again for my own formatted JSON Data. But the problem in my code is that it shows only the last data from the list, Not the entire data.The foreach loop is not working.

My Code to Deserialize and serialize json object is look like this-

[SwaggerResponse(HttpStatusCode.OK, "A", typeof(PoiImageAnswer))]
    [SwaggerResponse(HttpStatusCode.BadRequest, "Empty Answer", typeof(ModelStateDictionary))]
    [SwaggerResponse(HttpStatusCode.InternalServerError, "No Response")]
    [HttpPost]
    [ActionName("Image")]
    public IHttpActionResult Image([FromBody] PoiImageRequest request)
    {
        var result = new PoiImageAnswer {TransactionID = request.TransactionID};



       using (WebClient client = new WebClient())
       {
        var response = client.DownloadString("https://en.wikipedia.org/w/api.php?format=json&action=query&redirects=1&generator=geosearch&prop=extracts|coordinates|pageimages&ggslimit=20&ggsradius=1000&ggscoord=52.5243700|13.4105300&&formatversion=2&exintro=1&explaintext=1&exlimit=20&coprop=type|dim|globe&colimit=20&piprop=thumbnail&pithumbsize=400&pilimit=20");
        var json = JsonConvert.DeserializeObject<RootObject>(response);

        List<PoiImageAnswer> poi = new List<PoiImageAnswer>();

        foreach (var page in json.query.pages)
          {

              try
               {

                var Img= page.thumbnail.source;
                result.Title = page.title;
                result.Height = page.thumbnail.height;
                result.Width = page.thumbnail.width;
                result.ImageData = string.Format("{0:X}.jpg", page.thumbnail.source.GetHashCode());
                result.TransactionID = request.TransactionID;
            }
            catch (Exception)
            {

            }

         }       
           return Ok(result);
         }

       }
    }

My C# class for json object is as below for understanding the code,

 public class PoiImageAnswer
 {
    public string ImageID { set; get; }
    public string Title { set; get; }
    public int Width { set; get; }
    public int Height { set; get; }
    public string ImageData { set; get; }
    public long TransactionID { set; get; }
 }


 public class Poi
 {
   public string Title { set; get; }
   public string Description { set; get; }
   public List<PoiImage> Images { set; get; }
   public string OpeningHours { set; get; }
   public double AirDistanceInKm { set; get; }
   public double Lon { set; get; }
   public double Lat { set; get; }
 }

  public class PoiImage
  {
   public string ImageID { set; get; }
  }

I am getting output like this which is the last object from the list-

{
"ImageID": null,
"Title": "1976 Conference of Communist and Workers Parties of Europe",
 "Width": 243,
 "Height": 400,
 "ImageData": "53E5DCF3.jpg",
 "TransactionID": 0

}

It is because result variable of type PoiImageAnswer is single object and not collection. If you need all items from list then you need collection where you will store formatted json object and then this collection you need to send as result. — Pankaj Kapare
– Pankaj Kapare, Commented Mar 9, 2016 at 17:18
@PankajKapare, Could you please explain me how can I do that. I am very new in this case. Thank you. — harry.luson
– harry.luson, Commented Mar 9, 2016 at 17:19
Harry, you need to brush up on Collections in .NET; the System.Collections.Generic namespace in particular in order to deal with lists. Good luck! — Moby's Stunt Double
– Moby's Stunt Double, Commented Mar 9, 2016 at 17:21
@Moby'sStuntDouble. Could you please explain a little bit more. Actually I am very new handling this case. — harry.luson
– harry.luson, Commented Mar 9, 2016 at 17:23
There you go, Harry. I gave you an answer with explanations of what I was speaking about above. — Moby's Stunt Double
– Moby's Stunt Double, Commented Mar 9, 2016 at 17:38

Moby's Stunt Double · Accepted Answer · 2016-03-09 18:21:10Z

1

You need code something like below. Note: I haven't tested it but it should work.

public IHttpActionResult Image([FromBody] PoiImageRequest request)
    {            
        var resultList = new List<PoiImageAnswer>();

        using (WebClient client = new WebClient())
        {
            var response = client.DownloadString("https://en.wikipedia.org/w/api.php?format=json&action=query&redirects=1&generator=geosearch&prop=extracts|coordinates|pageimages&ggslimit=20&ggsradius=1000&ggscoord=52.5243700|13.4105300&&formatversion=2&exintro=1&explaintext=1&exlimit=20&coprop=type|dim|globe&colimit=20&piprop=thumbnail&pithumbsize=400&pilimit=20");
            var json = JsonConvert.DeserializeObject<RootObject>(response);

            foreach (var page in json.query.pages)
            {

                try
                {
                    var result = new PoiImageAnswer();
                    var Img = page.thumbnail.source;
                    result.Title = page.title;
                    result.Height = page.thumbnail.height;
                    result.Width = page.thumbnail.width;
                    result.ImageData = string.Format("{0:X}.jpg", page.thumbnail.source.GetHashCode());
                    result.TransactionID = request.TransactionID;
                    resultList.Add(result);
                }
                catch (Exception)
                {

                }

            }
            return Ok(resultList);
        }

    }

edited Mar 9, 2016 at 18:21

Moby's Stunt Double

2,5401 gold badge18 silver badges32 bronze badges

answered Mar 9, 2016 at 17:33

Pankaj Kapare

7,8725 gold badges42 silver badges58 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

harry.luson Over a year ago

Thnk you very much. your code is working. But I have a small question that how can I set then var result = new PoiImageAnswer {TransactionID = request.TransactionID}; because in your code you wrote var resultList = new List<PoiImageAnswer>();

Pankaj Kapare Over a year ago

result.TransactionID = request.TransactionID; This line is already updating TransactionId so you don't need to initialize it while declaring it.

harry.luson Over a year ago

Thank you very much for explanation

Moby's Stunt Double · Accepted Answer · 2016-03-09 17:40:16Z

1

You need to compile and send back a List. You are doing a foreach loop, but not compiling the list and sending it to the View.

Your code should look something like this (untested):

[SwaggerResponse(HttpStatusCode.OK, "A", typeof(List<PoiImageAnswer>))]
[SwaggerResponse(HttpStatusCode.BadRequest, "Empty Answer", typeof(ModelStateDictionary))]
[SwaggerResponse(HttpStatusCode.InternalServerError, "No Response")]
[HttpPost]
[ActionName("Image")]
public IHttpActionResult Image([FromBody] PoiImageRequest request)
{
    using (WebClient client = new WebClient())
    {
        var response = client.DownloadString("https://en.wikipedia.org/w/api.php?format=json&action=query&redirects=1&generator=geosearch&prop=extracts|coordinates|pageimages&ggslimit=20&ggsradius=1000&ggscoord=52.5243700|13.4105300&&formatversion=2&exintro=1&explaintext=1&exlimit=20&coprop=type|dim|globe&colimit=20&piprop=thumbnail&pithumbsize=400&pilimit=20");
        var json = JsonConvert.DeserializeObject<RootObject>(response);
        List<PoiImageAnswer> poi = new List<PoiImageAnswer>();
        foreach (var page in json.query.pages)
        {
            try
            {
                poi.Add(new PoiImageAnswer {
                    TransactionID = request.TransactionID,
                    Title = page.title,
                    Height = page.thumbnail.height,
                    Width = page.thumbnail.width,
                    ImageData = string.Format("{0:X}.jpg", page.thumbnail.source.GetHashCode())
                });
            }
            catch (Exception)
            {

            }
        }       
        return Ok(poi);
    }
}

N.B.

The change in your SwaggerResponse type.
The poi.Add() in your try statement.
The return of poi - your answer list, not result.
You will need to add a using at the top of the controller for System.Collections.Generic if there isn't already one there.

Good luck with your app!

edited Mar 9, 2016 at 17:40

answered Mar 9, 2016 at 17:34

Moby's Stunt Double

2,5401 gold badge18 silver badges32 bronze badges

3 Comments

harry.luson Over a year ago

Thank you very much for explanation: Now I got a result. But I have a small question what should I do in this line var result = new PoiImageAnswer {TransactionID = request.TransactionID};

Moby's Stunt Double Over a year ago

It's already being set, harry, look in the try. You don't need that original line at the top.

harry.luson Over a year ago

Thanks a lot. Yes now I understand.

Collectives™ on Stack Overflow

Looping does not work in JSON serialization using Web Api Controller ASP.NET MVC

2 Answers 2

3 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related