如何在C＃中正确反序列化JSON

Question

I am trying to deserialize the Supreme New York JSON but I am getting an error.

I used json2csharp.com to convert the Json into classes.

Then I summarised them all into one called items

namespace SUPBOTTESTING
{
    public class items
    {
        public string name { get; set; }
        public int id { get; set; }
        public string image_url { get; set; }
        public string image_url_hi { get; set; }
        public int price { get; set; }
        public int sale_price { get; set; }
        public bool new_item { get; set; }
        public int position { get; set; }
        public string category_name { get; set; }
        public int price_euro { get; set; }
        public int sale_price_euro { get; set; }
    }
}

using System;
using System.Net;
using System.Web.Script.Serialization;

namespace SUPBOTTESTING
{
    class Program
    {
        public static void Main()
        {
            {
                string shop_json = new WebClient().DownloadString("https://www.supremenewyork.com/mobile_stock.json");
                JavaScriptSerializer shop_object = new JavaScriptSerializer();
                items[] shirt_stock = shop_object.Deserialize<items[]>(shop_json);
                Console.WriteLine(shirt_stock[1]);

            }
        }
    }
}

I am getting the error:

Default constructor not found for type SUPBOTTESTING.items[]

Answer 1

Well you do not need to specify a default constructor. What is wrong is, i think you didn't check the json data properly. Because your items class is not in the first level of json. You need to create a couple of classes to be more accurate on deserializing.

First of all you need to know that this json file has a lot of bad-smells and bad-practices on it.

Note that you need to install Newtonsoft.Json before going further. It is much more convenient way to deserialize a json into C# classes.

Yet, i wrote a proper way of deserializing it:

public class BaseItem
{

    public string Name { get; set; }
    public int Id { get; set; }
    public string Image_url { get; set; }
    public string Image_url_hi { get; set; }
    public int Price { get; set; }
    public int Sale_price { get; set; }
    public bool New_item { get; set; }
    public int Position { get; set; }
    public string Category_name { get; set; }
    public int Price_euro { get; set; }
    public int Sale_price_euro { get; set; }
}
public class Shirt : BaseItem { }
public class Bag : BaseItem { }
public class Accessory : BaseItem { }
public class Pant : BaseItem { }
public class Jacket : BaseItem { }
public class Skate : BaseItem { }
public class Hat : BaseItem { }
public class Sweatshirt : BaseItem { }
public class TopsSweater : BaseItem { }
public class New : BaseItem { }
public class RootObject
{
    public List<object> Unique_image_url_prefixes { get; set; }
    public ProductsAndCategories Products_and_categories { get; set; }
    public string Release_date { get; set; }
    public string Release_week { get; set; }
}
public class ProductsAndCategories
{
    public List<Shirt> Shirts { get; set; }
    public List<Bag> Bags { get; set; }
    public List<Accessory> Accessories { get; set; }
    public List<Pant> Pants { get; set; }
    public List<Jacket> Jackets { get; set; }
    public List<Skate> Skate { get; set; }
    public List<Hat> Hats { get; set; }
    public List<Sweatshirt> Sweatshirts { get; set; }
    [JsonProperty("Tops/Sweaters")]
    public List<TopsSweater> TopsSweaters { get; set; }
    public List<New> New { get; set; }
}

First of all, all of your items are have the same properties on them, yet, they all marked as different properties. So that, i created a BaseItem class and other empty classes which are inherited from that.

Also you need other 2 classes -which are RootObject and ProductsAndCategories - to provide data on them. Note that there is a JsonProperty("blabla") on the TopsSweaters property. Because, in json file it is Tops/Sweaters , and you can not use that name on a C# property. That is the attribute for using that kind of different property names.

Then you can populate your object like this:

static void Main(string[] args)
    {
        var jsonData = "https://www.supremenewyork.com/mobile_stock.json";
        string shopJson = new WebClient().DownloadString(jsonData);
        RootObject shirtStock = JsonConvert.DeserializeObject<RootObject>(shopJson); //All json data is in this variable
        Console.WriteLine(shirtStock.Products_and_categories.Shirts[1]);
    }

Answer 2

Ok here is the solution. You have the correct idea but you need to understand the structure of your Json data.

You are deserializing it into an array of Object whereas your Json data returned itself is not an Array or a List. It contains child nodes that are an array so you need to structure your Object accordingly to get a successful breakdown of data.

Here I have used Newtonsoft to deserialise the Json data into an Object.

I have tested the code and it returns a list of Shirts

static void Main(string[] args)
{
     var shop_json = new WebClient().DownloadString("https://www.supremenewyork.com/mobile_stock.json");
     var shirt_stock = JsonConvert.DeserializeObject<StockObject>(shop_json);

     // Picking shirts to demonstrate how to display values for all shirts
     var shirts = shirt_stock.products_and_categories.Shirts;
     foreach (var shirt in shirts)
     {
         var shirtBuilder = new StringBuilder();
         shirtBuilder.AppendLine($"Name: {shirt.name}");
         shirtBuilder.AppendLine($"ID: {shirt.id.ToString()}");
         shirtBuilder.AppendLine($"New Item: {shirt.new_item.ToString()}");
         shirtBuilder.AppendLine($"Category Name: {shirt.category_name}");
         Console.WriteLine(shirtBuilder);
     }
}

public class StockObject
{
    public ProductsCats Products_and_categories { get; set; }
}

public class ProductsCats
{
    public Details[] Shirts { get; set; }
    public Details[] Bags { get; set; }
    public Details[] Accessories { get; set; }
    public Details[] Pants { get; set; }
    public Details[] Jackets { get; set; }
    public Details[] Skates { get; set; }
    public Details[] Hats { get; set;}
    public Details[] Sweatshirts { get; set;}
    [JsonProperty("Tops/Sweaters")]
    public Details[] TopsSweaters { get;set;}
    public Details[] New { get; set; }
}

public class Details
{
    public string name { get; set; }
    public int id { get; set; }
    public string image_url { get; set; }
    public string image_url_hi { get; set; }
    public int price { get; set; }
    public int sale_price { get; set; }
    public bool new_item { get; set; }
    public int position { get; set; }
    public string category_name { get; set; }
    public int price_euro { get; set; }
    public int sale_price_euro { get; set; }
}

You see what I have done here?

So your Json data contains a parent node products_and_categories and its child node contains an array of Shirts which is what you are after?

StockObject class contains the Parent property called Products_and_categories of type object ProductsCats .

ProductsCats Object contains the property Shirts of type Details which is an array and will be used during the deserialising process.

Hope this helps?

Answer 3

Your problem is that youre using a class to load the JSON data in, where you should use a struct, alternatively you can also create a constructor that takes no arguments and sets all variables to default values, which is a lot of work so just replace class with struct :

public struct Items
{
    public string Name { get; set; }
    public int Id { get; set; }
    public string Image_Url { get; set; }
    public string Image_Url_Hi { get; set; }
    public int Price { get; set; }
    public int Sale_Price { get; set; }
    public bool New_item { get; set; }
    public int Position { get; set; }
    public string Category_Name { get; set; }
    public int Price_Euro { get; set; }
    public int Sale_Price_Euro { get; set; }
}

Also please stick to C# naming conventions, you should be able to do this since most JSON parsers are case insensitive by default.

Some more info: A class doesnt really has a proper default constructor if you dont define one, where as a struct always has a default constructor, so when the JSON parser wants to init your class it cant because a default constructor isnt definded.

Answer 4

 static void Main(string[] args)
    {
        string shop_json = new WebClient().DownloadString("https://www.supremenewyork.com/mobile_stock.json");

        JavaScriptSerializer shop_object = new JavaScriptSerializer();
        var shirt_stock = shop_object.Deserialize<NewYarkItems>(shop_json);

        var v = shirt_stock;

    }


public class NewYarkItems
{
    public dynamic unique_image_url_prefixes { get; set; }
    public products_and_categories products_And_Categories { get; set; }
    public string release_date { get; set; }
    public string release_week { get; set; }
}

public class products_and_categories
{
    public List<items> Jackets { get; set; }
}


public class items
{
    public string name { get; set; }
    public int id { get; set; }
    public string image_url { get; set; }
    public string image_url_hi { get; set; }
    public int price { get; set; }
    public int sale_price { get; set; }
    public bool new_item { get; set; }
    public int position { get; set; }
    public string category_name { get; set; }
    public int price_euro { get; set; }
    public int sale_price_euro { get; set; }
}