How to deserialize encapsulated table of objects in .NET Core from JSON file?

Question

I want to retrieve a collection of football leagues from an external api. The response from the server comes as shown below:

{
"api": {
    "results": 1496,
    "leagues": [
        {
            "league_id": 1,
            .....

The returned object constists of an "api" field which hold "results" and "leagues". I would like deserialize the code and map it to League class objects in my code.

var jsonString = await ExecuteUrlAsync(filePath, url);

var results = JsonConvert.DeserializeObject<IEnumerable<LeagueEntity>>(jsonString);

jsonString is correct, but when the program hits second line I get an exception:

Cannot deserialize the current JSON object (e.g. {\"name\":\"value\"}) into type 'System.Collections.Generic.IEnumerable".

I need to get to the "leagues" field in JSON file, and ignore the rest of the response. How to achieve that?

Is it `Syste.Text.Json` or `Json.NET` api? How does `LeagueEntity` look like? — Pavel Anikhouski, Mar 16 '20 at 19:07
post a complete json sample and i could tell you how to do it with strongly typed model — Jonathan Alfaro, Mar 17 '20 at 00:03

score 1 · Accepted Answer · answered Mar 16 '20 at 19:12

Assuming your LeagueEntity corresponds to the api.leagues[*] objects, you can use JsonConvert.DeserializeAnonymousType() to pick out and deserialize the interesting portions of the JSON:

var leagues = JsonConvert.DeserializeAnonymousType(jsonString, 
                                                   new { api = new { leagues = default(List<LeagueEntity>) } })
    ?.api?.leagues;

This avoids the need to create an explicit data model for the api.leagues container objects. It should also be more efficient than pre-loading into a JToken hierarchy, then as a second step selecting and deserializing the api.leagues array.

Demo fiddle here.

(Alternatively, you could auto-generate a complete data model for the entire JSON using one of the answers from How to auto-generate a C# class file from a JSON string.)

How to deserialize encapsulated table of objects in .NET Core from JSON file?

1 Answers1