JSON.NET get specific items from string

Question

I have a string called rawJsonPostCodeString that looks like the following JSON.

{
    "status": 200,
    "result": {
        "postcode": "SW1A 1AA",
        "quality": 1,
        "eastings": 529090,
        "northings": 179645,
        "country": "England",
        "nhs_ha": "London",
        "longitude": -0.141588,
        "latitude": 51.501009,
        "european_electoral_region": "London",
        "primary_care_trust": "Westminster",
        "region": "London",
        "lsoa": "Westminster 018C",
        "msoa": "Westminster 018",
        "incode": "1AA",
        "outcode": "SW1A",
        "parliamentary_constituency": "Cities of London and Westminster",
        "admin_district": "Westminster",
        "parish": "Westminster, unparished area",
        "admin_county": null,
        "admin_ward": "St James's",
        "ced": null,
        "ccg": "NHS Central London (Westminster)",
        "nuts": "Westminster",
        "codes": {
            "admin_district": "E09000033",
            "admin_county": "E99999999",
            "admin_ward": "E05000644",
            "parish": "E43000236",
            "parliamentary_constituency": "E14000639",
            "ccg": "E38000031",
            "ced": "E99999999",
            "nuts": "UKI32"
        }
    }
}

I also have a class called PostCodeLocation that looks like the below:

class PostCodeLocation
{        
    public double longitude { get; set; }
    public double latitude { get; set; }
}

I have been using Json.Net to parse this data and then assign it to two items in the class.

Previously I have been using a code like the below to fetch data from a list with multiple results but when I try adapting this to read from my JSON for the post codes it throws an error on the JArray.Parse line for the format being invalid. I have not done any work with JSON before so I am unsure of the best way to process it.

  public List<PostCodeLocation> ProcessJSONPostCodeLocation(string JSonPostCodes)
    {
        JArray PCDetails = JArray.Parse(JSonPostCodes);
        List<JToken> results = PCDetails.Children().ToList();
        List<PostCodeLocaton> PCResults = new List<PostCodeLocation>();
        foreach (JToken result in results)
        {
            PCResults.Add(result.ToObject<PostCodeLocation>());
        }
        return PCResults;
    }

If anyone has any tips it would be greatly appreciated.

Answer 1

First, your json is not valid. You have this:

{
    "status": 200,
    "result" {
        "postcode": "SW1A 1AA"
        "longitude":-0.141588
        "latitude":51.501009
    }
}

To make it valid json, it needs to look like this:

{
    "status": 200,
    "result": {
        "postcode": "SW1A 1AA",
        "longitude":-0.141588,
        "latitude":51.501009
    }
}

(and that's assuming that result is not an array. If it IS an array, you will need [].)

There is a handy online tool I use all the time to make sure my json strings are valid: https://jsonformatter.curiousconcept.com/

Now that we have valid json to work with, we need a model to match it. Here's another handy online tool that converts your json string into c# objects: http://json2csharp.com/

Using that tool, we get this:

    public class RootObject
    {
        public int Status { get; set; }
        public Result Result { get; set; }
    }

    public class Result
    {
        public string Postcode { get; set; }
        public double Longitude { get; set; }
        public double Latitude { get; set; }
    }

And now, creating an instance of RootObject is as simple as:

RootObject rootObject = Newtonsoft.Json.JsonConvert.DeserializeObject<RootObject>(rawJsonPostCodeString );