c# reading json file, 'Unexpected character encountered while parsing value: s. Path '', line 0, position 0.'

Question

I'm currently using Blazor WebAssembly. This is the error i'm getting when I try to Deserialize with the nuGet Newtonsoft.Json. 'Unexpected character encountered while parsing value: s. Path '', line 0, position 0.'

This is my JSON file :

[{
    "Id": 1,
    "Brand": "Aprilia",
    "Modele": "RS 660",
    "CC": 660,
    "Nb Cylindre": 2,
    "Config cylindre": "ligne",
    "Couple": "66 Nm 8500",
    "Puissance (kW)": "XXX",
    "Puissance (cv)": "100 cv 10500",
    "Poids sec (kg)": 169,
    "Date sortie": 2023
}, {
    "Id": 2,
    "Brand": "Aprilia",
    "Modele": "Tuono 660",
    "CC": 660,
    "Nb Cylindre": 2,
    "Config cylindre": "ligne",
    "Couple": "66 Nm 8500",
    "Puissance (kW)": "XXX",
    "Puissance (cv)": "95 cv 10500",
    "Poids sec (kg)": 183,
    "Date sortie": 2023
}]

And my **object **:

public class MotoDTO
    {
        public int Id { get; set; }
        public string Brand { get; set; }
        public string Modele { get; set; }
        public int CC { get; set; }
        public int NbCylindre { get; set; }
        public string ConfigCylindre { get; set; }
        public string Couple { get; set; }
        public string PuissanceKW { get; set; }
        public string PuissanceCv { get; set; }
        public int PoidsSecKg { get; set; }
        public int DateSortie { get; set; }
    }

And finaly, this is where the **error **occurs :

            try
            {
                var serializer = new JsonSerializer();

                using (var sr = new StringReader(jsonFile))
                {
                    using (var jsonTextReader = new JsonTextReader(sr))
                    {
                        jsonTextReader.SupportMultipleContent = true;
            here -->    while (jsonTextReader.Read())
                        {
                            var moto = serializer.Deserialize<MotoDTO>(jsonTextReader);
                            _motos.Add(moto);
                        }

                    }
                }
            }
            catch (Exception ex)
            {
                string msg = ex.Message;
            }

Could somebody help me ? Thanks

I got the code here https://stackoverflow.com

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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            string json = @"
{'ItemName':'8','Id':1}
{'ItemName':'9','Id':2}
";

            var items = new List<Item>();

            var serializer = new JsonSerializer();

            using (var sr = new StringReader(json))
            {
                using (var jsonTextReader = new JsonTextReader(sr))
                {
                    jsonTextReader.SupportMultipleContent = true;
                    while (jsonTextReader.Read())
                    {
                        var data = serializer.Deserialize<Item>(jsonTextReader);
                        items.Add(data);
                    }

                }
            }

            foreach (Item item in items)
            {
                Console.WriteLine($"{item.Id}: {item.ItemName}");
            }
        }
    }

    public class Item
    {
        public string ItemName { get; set; }
        public int Id { get; set; }
    }
}

Answer 1

You Dto's property names do not match the json data. And you want to deserialize to a single Dto but your json data is an array. Here's who you can deszerialize it:

 public void Deserialize()
    {
        string jsonData = @"[
    {
        ""Id"": 1,
        ""Brand"": ""Aprilia"",
        ""Modele"": ""RS 660"",
        ""CC"": 660,
        ""Nb Cylindre"": 2,
        ""Config cylindre"": ""ligne"",
        ""Couple"": ""66 Nm 8500"",
        ""Puissance (kW)"": ""XXX"",
        ""Puissance (cv)"": ""100 cv 10500"",
        ""Poids sec (kg)"": 169,
        ""Date sortie"": 2023
    },
    {
        ""Id"": 2,
        ""Brand"": ""Aprilia"",
        ""Modele"": ""Tuono 660"",
        ""CC"": 660,
        ""Nb Cylindre"": 2,
        ""Config cylindre"": ""ligne"",
        ""Couple"": ""66 Nm 8500"",
        ""Puissance (kW)"": ""XXX"",
        ""Puissance (cv)"": ""95 cv 10500"",
        ""Poids sec (kg)"": 183,
        ""Date sortie"": 2023
    }
    ]";

        var obj = JsonConvert.DeserializeObject<List<MotoDTO>>(jsonData);

    }

The adjusted DTO

using Newtonsoft.Json;

  public class MotoDTO
    {
        public int Id { get; set; }
        public string Brand { get; set; }
        public string Modele { get; set; }
        public int CC { get; set; }

        [JsonProperty("Nb Cylindre")]
        public int NbCylindre { get; set; }

        [JsonProperty("Config cylindre")]
        public string ConfigCylindre { get; set; }
        public string Couple { get; set; }

        [JsonProperty("Puissance (kW)")]
        public string PuissanceKW { get; set; }

        [JsonProperty("Puissance (cv)")]
        public string PuissanceCv { get; set; }

        [JsonProperty("Poids sec (kg)")]
        public int PoidsSecKg { get; set; }

        [JsonProperty("Date sortie")]
        public int DateSortie { get; set; }
    }

Now in order to fetch the file from the wwwroot folder you have to use the httpClient

@inject HttpClient Client

@code
{

    private List<MotoDTO> motos;

    protected override async Task OnInitializedAsync()
    {
        motos = await LoadMotosFromJsonAsync();
    }

    private async Task<List<MotoDTO>> LoadMotosFromJsonAsync()
    {
        var response = await Client.GetAsync("sample-data/DB_Moto.json");

        if (response.IsSuccessStatusCode)
        {
            var content = await response.Content.ReadAsStringAsync();
            return JsonConvert.DeserializeObject<List<MotoDTO>>(content);
        }
        else
        {
            return new List<MotoDTO>();
        }
    }
}

please make sure the HttpClient is registerd in the app

public static async Task Main(string[] args)
        {
            var builder = WebAssemblyHostBuilder.CreateDefault(args);
            builder.RootComponents.Add<App>("#app");
            builder.RootComponents.Add<HeadOutlet>("head::after");
            builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

            await builder.Build().RunAsync();
        }