.NET 8: Serialization Improvements

The System.Text.Json namespace provides functionality for serializing to and deserializing from JSON. In .NET 8, there have been many improvements to the System.Text.Json serialization and deserialization functionality.

Source generator

.NET 8 includes enhancements of the System.Text.Json source generator that are aimed at making the Native AOT experience on par with the reflection-based serializer. This is important because now you can select the source generator for System.Text.Json. To see a comparison of Reflection versus source generation in System.Text.Json, check out the comparison documentation.

Interface hierarchies

.NET 8 adds support for serializing properties from interface hierarchies. Here is a code sample that shows this feature.

ICar car = new MyCar { Color = "Red", NumberOfWheels = 4 };
JsonSerializer.Serialize(car); // {"Color":"Red","NumberOfWheels":4}

public interface IVehicle
    public string Color { get; set; }

public interface ICar : IVehicle
    public int NumberOfWheels { get; set; }

public class MyCar : ICar
    public string Color { get; set; }
    public int NumberOfWheels { get; set; }

Naming policies

Two new naming policies snake_case and kebab-case have been added. You can use them as shown below:

var options = new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower };
JsonSerializer.Serialize(new { CreationTime = new DateTime(2023,11,6) }, options); // {"creation_time":"2023-11-06T00:00:00"}

Read-only properties

With .NET 8, you can deserialize onto read-only fields or properties. This feature can be globally enabled by setting PreferredObjectCreationHandling to JsonObjectCreationHandling.Populate. You can also enable this feature for a class or one of its members by adding the [JsonObjectCreationHandling(JsonObjectCreationHandling.Populate)] attribute. Here is a sample:

using System.Text.Json;
using System.Text.Json.Serialization;

var book = JsonSerializer.Deserialize<Book>("""{"Contributors":["John Doe"],"Author":{"Name":"Sample Author"}}""")!;

class Author
    public required string Name { get; set; }

class Book
    // Both of these properties are read-only.
    public List<string> Contributors { get; } = new();
    public Author Author { get; } = new() {Name = "Undefined"};

Before .NET 8, the output was like this:


With .NET 8, the output now looks like this:

{"Contributors":["John Doe"],"Author":{"Name":"Sample Author"}}

Disable reflection-based default

One of the nice features about Serialization is, now you can disable using the reflection-based serializer by default. To disable default reflection-based serialization, set the JsonSerializerIsReflectionEnabledByDefault MSBuild property to false in your project file.

Streaming deserialization APIs

.NET 8 includes new IAsyncEnumerable<T> streaming deserialization extension methods. The new extension methods invoke streaming APIs and return IAsyncEnumerable<T>. Here is a sample code that uses this new feature.

const string RequestUri = "https://yourwebsite.com/api/saas/tenants?skipCount=0&maxResultCount=10";
using var client = new HttpClient();
IAsyncEnumerable<Tenant> tenants = client.GetFromJsonAsAsyncEnumerable<Tenant>(RequestUri);

await foreach (Tenant tenant in tenants)
    Console.WriteLine($"* '{tenant.name}' uses '{tenant.editionName
}' edition");

I have mentioned some of the items for Serialization Improvements in .NET 8. If you want to check the full list, you can read it in the .NET 8's What's new document.