Deserializing JSON to a C# class returns null

Question

I'm trying to deserialize a JSON file to a c# class. However, my deserialize method always returns null. My JSON file looks like this-

{
  "Products": [
    {
      "ProductID": 994,
      "Name": "LL Bottom Bracket",
      "ProductNumber": "BB-7421",
      "ProductCategoryID": 9,
      "ProductCategory": "Bottom Brackets",
      "ProductModelID": 95,
      "Description": "Chromoly steel."
    },
    {
      "ProductID": 995,
      "Name": "ML Bottom Bracket",
      "ProductNumber": "BB-8107",
      "ProductCategoryID": 9,
      "ProductCategory": "Bottom Brackets",
      "ProductModelID": 96,
      "Description": "Aluminum alloy cups; large diameter spindle."
    }
  ]
}

I'm trying to serialize it to below class-

public class Product
    {
        [JsonProperty("ProductID")]
        public long ProductId { get; set; }

        [JsonProperty("Name")]
        public string Name { get; set; }

        [JsonProperty("ProductNumber")]
        public string ProductNumber { get; set; }

        [JsonProperty("ProductCategoryID")]
        public long ProductCategoryId { get; set; }

        [JsonProperty("ProductCategory")]
        public string ProductCategory { get; set; }

        [JsonProperty("ProductModelID")]
        public long ProductModelId { get; set; }

        [JsonProperty("Description")]
        public string Description { get; set; }

        [JsonProperty("Color", NullValueHandling = NullValueHandling.Ignore)]
        public string Color { get; set; }
    }
    public partial class Products
    {
        [JsonProperty("Products")]
        public IEnumerable<Product> ProductsProducts { get; set; }
    }

And finally, I'm using this code to deserialize it, however it returns null for some reason. Can someone please help?

public Products Get()
        {
            var jsonString = IO.File.ReadAllText("ProductsData.json");
            var products = JsonSerializer.Deserialize<Products>(jsonString);
            
            return products;
        }

It may be an issue with using IEnumerable<Product> for the "Products" property - try either making it an ICollection<Product> or List<Product>, if that doesn't work. For a more elegant solution, I believe there's a way to set a default collection implementation but I don't know what it is off the top of my head. — eouw0o83hf
– eouw0o83hf, Commented Jan 25, 2021 at 17:41
I've tried with List and ICollection but it still doesn't work unfortunately. — Dhawal Dhingra
– Dhawal Dhingra, Commented Jan 25, 2021 at 17:45

Heinzi · Accepted Answer · 2021-01-25 17:57:36Z

14

Cause

You are using the JsonProperty attribute from the Netwonsoft.Json package, but the built-in .NET Core/5 deserializer from the System.Text.Json namespace.

How do I know that? Newtonsoft.Json does not have a JsonSerializer.Deserialize overload which takes a single string, and .NET does not contain a JsonPropertyAttribute.

Those two are not compatible. The .NET deserializer ignores your [JsonProperty("Products")] attribute, does not find a propery named ProductsProducts in your JSON and, thus, yields null for that property.

Fix

To use the deserializer from the Newtonsoft.Json package instead, replace

var products = JsonSerializer.Deserialize<Products>(jsonString);

with

var products = JsonConvert.DeserializeObject<Products>(jsonString);

Here is a working fiddle with your code: https://dotnetfiddle.net/27Tz4t

edited Jan 25, 2021 at 17:57

answered Jan 25, 2021 at 17:46

Heinzi

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4 Comments

Dhawal Dhingra Over a year ago

Thanks, that solves it. But lets say, for some reason I didn't to use Newtonsoft.Json, how'd I go about deserializing it?

Hazaaa Over a year ago

Then change attribute name to "JsonPropertyName" that is in System.Text.Json.

Eduard Over a year ago

This solves it for this specific case! But in my case, I had to add JsonPropertyName value with lower case instead of uppercase. So instead of JsonPropertyName("ProductName") I had to write JsonPropertyName("productName"). Maybe because of the JsonSerializerSettings that were specifying CamelCase and JsonPropertyName should override that.

crakama Over a year ago

The solution from @Eduard helped solve my problem. That is using "using System.Text.Json.Serialization" with lowercase in JsonPropertyName as "JsonPropertyName("productName")"

derodevil · Accepted Answer · 2021-01-25 18:01:46Z

5

Using NewtonsoftJson

var products = JsonConvert.DeserializeObject<Products>(jsonString);

Using System.Text.Json

var products = JsonSerializer.Deserialize<Products>(jsonString);
public partial class Products
{
    [System.Text.Json.Serialization.JsonPropertyName("Products")]
    public IEnumerable<Product> ProductsProducts { get; set; }
}

answered Jan 25, 2021 at 18:01

derodevil

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Comments

Daniel · Accepted Answer · 2021-01-25 18:23:26Z

if you have the json response, only use this site for convert Json to c# class

// Root myDeserializedClass = JsonConvert.DeserializeObject<Root>(myJsonResponse); 
    public class Product    {
        public int ProductID { get; set; } 
        public string Name { get; set; } 
        public string ProductNumber { get; set; } 
        public int ProductCategoryID { get; set; } 
        public string ProductCategory { get; set; } 
        public int ProductModelID { get; set; } 
        public string Description { get; set; } 
    }

    public class Root    {
        public List<Product> Products { get; set; } 
    }

public Products Get()
        {
            var jsonString = IO.File.ReadAllText("ProductsData.json");
            var products = JsonSerializer.Deserialize<Root>(jsonString);
            
            return products;
        }

or use visual studio option Edit-->Paste Special-->Paste JSON as Classes

 public class Rootobject
        {
            public Product[] Products { get; set; }
        }

        public class Product
        {
            public int ProductID { get; set; }
            public string Name { get; set; }
            public string ProductNumber { get; set; }
            public int ProductCategoryID { get; set; }
            public string ProductCategory { get; set; }
            public int ProductModelID { get; set; }
            public string Description { get; set; }
        }




public Products Get()
            {
                var jsonString = IO.File.ReadAllText("ProductsData.json");
                var products = JsonSerializer.Deserialize<Rootobject>(jsonString);
                
                return products;
            }

crakama · Accepted Answer · 2024-01-09 08:11:17Z

0

using System.Text.Json;

According to the offcical microsoft documentation (https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/customize-properties?pivots=dotnet-8-0), "The web default naming policy is camel case."

    JsonSerializerOptions options = new(JsonSerializerDefaults.Web)
    {
        WriteIndented = true
    };

In .NET 8, one can specify the naming policy that JSON can use when serializing/Decerializing

var test  = new HttpResponseMessage
{
    Content = JsonContent.Create(jsonBody, options: new JsonSerializerOptions { DictionaryKeyPolicy = JsonNamingPolicy.CamelCase }),
    StatusCode = httpStatusCode
};

answered Jan 9, 2024 at 8:11

crakama

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