Json 反序列化创建空对象

Question

The json can be found here: https://www.googleapis.com/books/v1/volumes?q=harry+potter

I'm having issues with deserializing the json into a list of book objects. I`m using two models, BookList and Books. Book list has a property called bookList which is just a list of Books.

When the code is run a Book List object is created, but its null.

Heres the code:

BookList.cs

using System.Collections.Generic;
using Newtonsoft.Json;

namespace HarryPotterBooksApp.Models
{
    public class BookList
    {
        [JsonProperty("items")]
        public List<Book> bookList {get;set;}
    }
}

Book.cs

using Newtonsoft.Json;

namespace HarryPotterBooksApp.Models
{
    public class Book
    {
      
        [JsonProperty("id")]
        public string id { get; set; }
        [JsonProperty("publisher")]
        public string publisher { get; set; }

    }
}

BookController.cs

namespace HarryPotterBooksApp.Controllers {
        public class BooksController: Controller {
            const string BASE_URL = "https://www.googleapis.com/books/v1/volumes?q=harry+potter";

            private readonly ILogger<BooksController> _logger;

            private readonly IHttpClientFactory _clientFactory;

            public BookList Books { get; set; }

            public bool GetBooksError { get; private set; }

            public BooksController (ILogger<BooksController> logger, IHttpClientFactory clientFactory)

            {

                _logger = logger;

                _clientFactory = clientFactory;

            }

            public async Task<IActionResult> Index ()

            {

                var message = new HttpRequestMessage ();

                message.Method = HttpMethod.Get;

                message.RequestUri = new Uri ($"{BASE_URL}api/Books");

                message.Headers.Add ("Accept", "application/json");

                var client = _clientFactory.CreateClient ();

                var response = await client.SendAsync (message);

                if (response.IsSuccessStatusCode) {

                    var responseString = await response.Content.ReadAsStringAsync();

                    Books = JsonConvert.DeserializeObject<BookList>(responseString);

                } else {

                    GetBooksError = true;

                    Books = new BookList();

                }

                return View (Books);

            }

Answer 1

Did you see the new library of Microsoft to deserialize JSON? It's called System.Text.Json, and it's amazing: https://docs.microsoft.com/fr-fr/dotnet/api/system.text.json?view=netcore-3.1

Also you have Json.NET by Newtonsoft: https://www.newtonsoft.com/json

Your JSON seem pretty complicate, a solution is to write each object and deserialze the JSON with each object (but it will be too long). Another solution is to build the representation by getting all the property.

Answer 2

You model doesn't match the source JSON, so that is going to be the first issue. The JSON has a single root object -- the root is not a list. That root contains kind, totalItems and items. The list of books is "items". You need a model that matches this. Likewise, the id is in the item (your Book) object, but the publisher is in a child object (volumeInfo). If you model doesn't match, then your call to DeserializeObject isn't going to work.

Given the complexity of the JSON being returned, perhaps the easiest way to ensure your model matches this JSON is to generate a model using a tool, such as https://json2csharp.com/ or https://app.quicktype.io/?l=csharp , that will build the C# model from example JSON. This will make sure your model matches the JSON and will provide a good starting point. You can always remove properties and children if you don't need them.