Parsing Multidimensional JSON Array with Newtonsoft Json.NET

Question

I have Json returning as the following:

[{"CreatedBy":"GIS_DB","CreatedDate":"3/8/2012 10:44:00 AM","Id":39,"ModifiedBy":"","ModifiedDate":"","Name":"CF-39","StatusId":1,"TrailCoordinates":[{"CreatedBy":"GIS_DB","CreatedDate":"3/8/2012 10:44:00 AM","Id":1637,"Latitude":32.76004207,"Longitude":-97.34006853,"ModifiedBy":"","ModifiedDate":"","SortOrder":1,"TrailId":39},{"CreatedBy":"GIS_DB","CreatedDate":"3/8/2012 10:44:00 AM","Id":1638,"Latitude":32.76004333,"Longitude":-97.34012121,"ModifiedBy":"","ModifiedDate":"","SortOrder":2,"TrailId":39}]},{"CreatedBy":"GIS_DB","CreatedDate":"3/8/2012 10:44:00 AM","Id":40,"ModifiedBy":"","ModifiedDate":"","Name":"CF-40","StatusId":1,"TrailCoordinates":[{"CreatedBy":"GIS_DB","CreatedDate":"3/8/2012 10:44:00 AM","Id":3755,"Latitude":32.76034332,"Longitude":-97.3402069,"ModifiedBy":"","ModifiedDate":"","SortOrder":1,"TrailId":40},{"CreatedBy":"GIS_DB","CreatedDate":"3/8/2012 10:44:00 AM","Id":3756,"Latitude":32.76019181,"Longitude":-97.3402448,"ModifiedBy":"","ModifiedDate":"","SortOrder":2,"TrailId":40}]}]

These are my classes...

public class Trails
{
    [MonoTouch.Foundation.Preserve]
    public Trails(){ TrailCoord = new List<trailcoords>();}

    [MonoTouch.Foundation.Preserve, JsonProperty("Name")]
    public string TrailName { get; set; }

    [MonoTouch.Foundation.Preserve, JsonProperty("StatusId")]
    public int StatusId { get; set; }

    [MonoTouch.Foundation.Preserve, JsonProperty("TrailCoordinates")]
    public List<trailcoords> TrailCoord { get; set; }
//  public trailcoords 

public Trails (string trailname, int statusid, List<trailcoords> trailcoord)
{
    TrailName = trailname;
        StatusId = statusid;
        TrailCoord = trailcoord;
    }       
}

public class trailcoords
{       
        [MonoTouch.Foundation.Preserve]
    public trailcoords(){}  
[MonoTouch.Foundation.Preserve, JsonProperty("TrailId")]
    public string TrailId { get; set; }     

    [MonoTouch.Foundation.Preserve, JsonProperty("Latitude")]
    public double Latitude { get; set; }    
[MonoTouch.Foundation.Preserve, JsonProperty("Longitude")]
    public double Longitude { get; set; }   

public trailcoords (string trailid, double latitude, double longitude)
{
    TrailId = trailid;
        Latitude = latitude;
        Longitude = longitude;
    }
}

List<Trails> Posts = JsonConvert.DeserializeObject<List<Trails>> ( json );

So from here I am not sure how I would access the Latitude and Longitude items in my list. I can access things like TrailName no problem but not sure what i'm doing wrong with the items in the array within the array. I would like to add them so that I can plot them as lines in a structure similar to this that I made (hardcoded values):

CLLocationCoordinate2D[] tmpTrail1 = new CLLocationCoordinate2D[]{
  new CLLocationCoordinate2D(32.751531, -97.361755),
  new CLLocationCoordinate2D(32.751451, -97.356625),
  new CLLocationCoordinate2D(32.751500, -97.332077),
};

CLLocationCoordinate2D[] tmpTrail2 = new CLLocationCoordinate2D[] {
  new CLLocationCoordinate2D(32.727353, -97.361139),
  new CLLocationCoordinate2D(32.747731, -97.359896),
  new CLLocationCoordinate2D(32.765735, -97.360360),
};

_trailOverlayPoints = new List<CLLocationCoordinate2D[]>();
_trailOverlayPoints.Add(tmpTrail1);
_trailOverlayPoints.Add(tmpTrail2);

L.B · Accepted Answer · 2012-04-02 16:18:24Z

12

Instead of declaring a lot of classes, I would parse the json string as follows

JArray jArr = (JArray)JsonConvert.DeserializeObject(jsonstr);
foreach (var item in jArr)
{
    foreach(var subitem in item["TrailCoordinates"])
    {
        Console.WriteLine(subitem["Longitude"] + " " + subitem["Latitude"]);
    }
}

If monotouch supports dynamic you can also write

dynamic jArr2 = JsonConvert.DeserializeObject(jsonstr);
foreach (dynamic item in jArr2)
{
    foreach (var subitem in item.TrailCoordinates)
    {
        Console.WriteLine(subitem.Longitude + " " + subitem.Latitude);
    }
}

You can even use Linq

JArray jArr = (JArray)JsonConvert.DeserializeObject(jsonstr);
var coords = jArr
            .Select(x => x["TrailCoordinates"])
            .SelectMany(x=>x)
            .Where(x => x["TrailId"].ToString() == "40")
            .Select(x => new { Lat = double.Parse(x["Latitude"].ToString()), Lon=double.Parse(x["Longitude"].ToString()) })
            .ToArray();

edited Apr 2, 2012 at 16:18

answered Apr 2, 2012 at 12:16

L.B

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1 Comment

k1komans Over a year ago

Thanks this is great! Using Linq would I be able to put in a "where" clause so that it only returns coordinates for a specific trail?

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