Object Serialization in C# (.NET): JSON, XML and Binary

Object Serialization in C# (.NET): JSON, XML and Binary

Serialization is the process of converting a complex object (or object graph) into a byte stream or text format (JSON, XML). This is necessary for saving an object's state to a file, transmitting data over a network (REST API, gRPC), or caching. The reverse process — deserialization — restores an object from its serialized representation. In the .NET ecosystem (including .NET Core and .NET 5/6/7/8), there are several built-in serialization mechanisms.

1. System.Text.Json — Modern JSON Serialization

Starting with .NET Core 3.0, Microsoft recommends using System.Text.Json as the primary way to work with JSON. The library is lightweight, high-performance, and does not require third-party dependencies (unlike Newtonsoft.Json).

Basic Serialization and Deserialization Example

using System;using System.Text.Json;

public class Person{    public string Name { get; set; }    public int Age { get; set; }    public List<string> Hobbies { get; set; }}

class Program{    static void Main()    {        var person = new Person        {            Name = "Alexey",            Age = 30,            Hobbies = new List<string> { "Reading", "Programming" }        };

        // Serialization        string json = JsonSerializer.Serialize(person);        Console.WriteLine(json);        // {"Name":"Alexey","Age":30,"Hobbies":["Reading","Programming"]}

        // Deserialization        Person restored = JsonSerializer.Deserialize<Person>(json);        Console.WriteLine(restored.Name); // Alexey    }}

Configuring Serialization with Attributes

You can control property names in JSON, ignore null values, or use custom converters:

using System.Text.Json.Serialization;

public class Product{    [JsonPropertyName("product_id")]    public int Id { get; set; }

    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]    public string? Description { get; set; }

    [JsonConverter(typeof(JsonStringEnumConverter))]    public Status Status { get; set; }}

public enum Status { Active, Inactive }

2. XmlSerializer — XML Serialization

The XmlSerializer class (namespace System.Xml.Serialization) is available in all .NET versions and is ideal for compatibility with legacy systems or configuration XML files.

Working with XmlSerializer Example

using System;using System.IO;using System.Xml.Serialization;

[XmlRoot("Employee")]public class Employee{    [XmlElement("FullName")]    public string Name { get; set; }

    [XmlAttribute("id")]    public int Id { get; set; }

    [XmlArray("Projects")]    [XmlArrayItem("Project")]    public List<string> Projects { get; set; }}

class Program{    static void Main()    {        var emp = new Employee        {            Id = 101,            Name = "Maria Ivanova",            Projects = new List<string> { "Alpha", "Beta" }        };

        var serializer = new XmlSerializer(typeof(Employee));        using (var writer = new StreamWriter("employee.xml"))        {            serializer.Serialize(writer, emp);        }

        // Deserialization        using (var reader = new StreamReader("employee.xml"))        {            Employee restored = (Employee)serializer.Deserialize(reader);            Console.WriteLine(restored.Name); // Maria Ivanova        }    }}

Important: XmlSerializer requires the class to have a public parameterless constructor, and the serializable properties must be public and have setters.

3. BinaryFormatter (deprecated, but mentioned for legacy)

Previously, System.Runtime.Serialization.Formatters.Binary.Bi