What is wrong with this JSON file? Can't be deserialized - json

Question

I have an issue with a JSON file, which is a list of country objects, as below:
{
"Countries": [
{
"Code": "AFG",
"Name": "Afghanistan",
"Population": 38928346
},
{
"Code": "ALA",
"Name": "Åland Islands",
"Population": 28007
},
{
"Code": "ALB",
"Name": "Albania",
"Population": 2877797
},
{
"Code": "DZA",
"Name": "Algeria",
"Population": 43851044
},
{
"Code": "ASM",
"Name": "American Samoa",
"Population": 55191
}
]
}
I am trying to use this code to read it and deserialize it into a List object:
Stream? countriesResourceStream = Assembly.GetExecutingAssembly().GetManifestResourceStream("MyProject.Countries.json");
if (countriesResourceStream == null)
{
return;
}
var countries = new List<Country>();
using (StreamReader reader = new StreamReader(countriesResourceStream))
{
var serializer = new JsonSerializer();
countries = serializer.Deserialize<List<Country>>(new JsonTextReader(reader));
}
However the serializer.Deserialize method throws the exception:
'Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[MyProject.Models.EntityFramework.Country]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.
To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.
What is the issue with my JSON? I have tried both Newtonsoft and System.Text.Json.

Answer 1

The problem is that your JSON does not represent a list of countries, it represents an object that contains a list of countries. You need another class:
class CountryListContainer
{
public List<Country> Countries { get; set; }
}
Deserialize into the container class and then you can get your country list from that:
using (StreamReader streamReader = new StreamReader(countriesResourceStream))
using (JsonTextReader jsonReader = new JsonTextReader(streamReader))
{
var serializer = new JsonSerializer();
countries = serializer.Deserialize<CountryListContainer>(jsonReader).Countries;
}
Fiddle: https://dotnetfiddle.net/5DM4il
Alternatively, you could change your JSON as #Charles Duffy suggested in the comments. If the JSON looked like this (without the outer object) then your existing code would work:
[
{
"Code": "AFG",
"Name": "Afghanistan",
"Population": 38928346
},
{
"Code": "ALA",
"Name": "Åland Islands",
"Population": 28007
},
{
"Code": "ALB",
"Name": "Albania",
"Population": 2877797
},
{
"Code": "DZA",
"Name": "Algeria",
"Population": 43851044
},
{
"Code": "ASM",
"Name": "American Samoa",
"Population": 55191
}
]
Fiddle: https://dotnetfiddle.net/gMHhcX