Serializing .NET Objects to JSON

JSON (JavaScript Object Notation) is a lightweight data-interchange format that’s easy for humans to read and write, and easy for machines to parse and generate. Often, you’ll need to convert .NET objects into JSON strings for purposes such as sending data over a network, storing data in a file, or interacting with web APIs. This tutorial covers several ways to accomplish this in .NET.

Choosing a JSON Serializer

Several options are available for serializing .NET objects to JSON. Historically, JavaScriptSerializer was used, but Microsoft now recommends using System.Text.Json for newer projects (.NET Core 3.0 and later, and .NET Standard 2.1 and later) or the popular third-party library Newtonsoft.Json for older .NET Framework versions. System.Text.Json is designed for high performance and security, while Newtonsoft.Json boasts a large feature set and widespread adoption.

Using System.Text.Json (Recommended for .NET Core 3.0+)

System.Text.Json is included in .NET Core 3.0 and later. If you’re targeting .NET Framework, you can add it as a NuGet package. This serializer leverages properties rather than fields for serialization.

using System;
using System.Text.Json;

public class MyDate
{
    public int year { get; set; }
    public int month { get; set; }
    public int day { get; set; }
}

public class Lad
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public MyDate DateOfBirth { get; set; }
}

class Program
{
    static void Main()
    {
        var lad = new Lad
        {
            FirstName = "Markoff",
            LastName = "Chaney",
            DateOfBirth = new MyDate
            {
                year = 1901,
                month = 4,
                day = 30
            }
        };

        var json = JsonSerializer.Serialize(lad);
        Console.WriteLine(json);
    }
}

This code snippet first defines two classes, MyDate and Lad. Then, an instance of Lad is created and populated with data. Finally, JsonSerializer.Serialize() is used to convert the Lad object into a JSON string, which is then printed to the console.

Using Newtonsoft.Json (JSON.NET)

Newtonsoft.Json is a widely used, feature-rich library for JSON serialization and deserialization. You can install it using the NuGet package manager.

using System;
using Newtonsoft.Json;

public class MyDate
{
    public int year { get; set; }
    public int month { get; set; }
    public int day { get; set; }
}

public class Lad
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public MyDate DateOfBirth { get; set; }
}

class Program
{
    static void Main()
    {
        var lad = new Lad
        {
            FirstName = "Markoff",
            LastName = "Chaney",
            DateOfBirth = new MyDate
            {
                year = 1901,
                month = 4,
                day = 30
            }
        };

        var json = JsonConvert.SerializeObject(lad);
        Console.WriteLine(json);
    }
}

This code is very similar to the System.Text.Json example, but uses JsonConvert.SerializeObject() from the Newtonsoft.Json library.

Using DataContractJsonSerializer (Older .NET Framework)

DataContractJsonSerializer is another option available in older .NET Framework versions. It requires the classes to be decorated with attributes to define the data contract. This method offers good control over the serialization process but is generally less performant than System.Text.Json or Newtonsoft.Json.

Choosing the Right Serializer

For new projects targeting .NET Core 3.0+ or .NET 5+, System.Text.Json is the recommended choice due to its performance and security benefits.
For older .NET Framework projects, Newtonsoft.Json is a solid option due to its wide adoption and rich feature set.
DataContractJsonSerializer can be used in older .NET Framework versions but is generally less efficient and requires more setup.