C# object serialization

Object serialization in C# is the process of converting an object into a stream of bytes for storage or transmission. The serialized data can be saved to files, databases, or sent over a network, and later deserialized back into objects.

C# provides several approaches for serialization, including binary serialization, XML serialization, and JSON serialization. Binary serialization preserves the complete object state and type information.

Syntax

For binary serialization using BinaryFormatter −

[Serializable]
public class ClassName {
   // class members
}

BinaryFormatter formatter = new BinaryFormatter();
formatter.Serialize(stream, objectInstance);

For deserialization −

ClassName obj = (ClassName)formatter.Deserialize(stream);

Using Binary Serialization

To serialize an object using BinaryFormatter, the class must be marked with the [Serializable] attribute. Here's a complete example −

Example

using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

[Serializable]
public class Employee {
   public int id;
   public string name;
   public int salary;

   public Employee(int id, string name, int salary) {
      this.id = id;
      this.name = name;
      this.salary = salary;
   }

   public void Display() {
      Console.WriteLine($"ID: {id}, Name: {name}, Salary: {salary}");
   }
}

public class SerializationExample {
   public static void Main() {
      // Serialization
      Employee emp = new Employee(001, "Jim", 30000);
      
      FileStream fStream = new FileStream("employee.dat", FileMode.Create);
      BinaryFormatter bFormat = new BinaryFormatter();
      
      bFormat.Serialize(fStream, emp);
      fStream.Close();
      Console.WriteLine("Employee object serialized successfully.");

      // Deserialization
      FileStream fStreamRead = new FileStream("employee.dat", FileMode.Open);
      Employee deserializedEmp = (Employee)bFormat.Deserialize(fStreamRead);
      fStreamRead.Close();
      
      Console.WriteLine("Deserialized Employee:");
      deserializedEmp.Display();
   }
}

The output of the above code is −

Employee object serialized successfully.
Deserialized Employee:
ID: 1, Name: Jim, Salary: 30000

Using JSON Serialization

Modern applications often prefer JSON serialization using System.Text.Json for better interoperability −

Example

using System;
using System.IO;
using System.Text.Json;

public class Person {
   public int Id { get; set; }
   public string Name { get; set; }
   public int Age { get; set; }

   public Person() { }

   public Person(int id, string name, int age) {
      Id = id;
      Name = name;
      Age = age;
   }
}

public class JsonSerializationExample {
   public static void Main() {
      Person person = new Person(1, "Alice", 25);

      // Serialize to JSON
      string jsonString = JsonSerializer.Serialize(person);
      Console.WriteLine("Serialized JSON:");
      Console.WriteLine(jsonString);

      // Save to file
      File.WriteAllText("person.json", jsonString);

      // Deserialize from JSON
      string jsonFromFile = File.ReadAllText("person.json");
      Person deserializedPerson = JsonSerializer.Deserialize<Person>(jsonFromFile);
      
      Console.WriteLine("\nDeserialized Person:");
      Console.WriteLine($"ID: {deserializedPerson.Id}, Name: {deserializedPerson.Name}, Age: {deserializedPerson.Age}");
   }
}

The output of the above code is −

Serialized JSON:
{"Id":1,"Name":"Alice","Age":25}

Deserialized Person:
ID: 1, Name: Alice, Age: 25

Comparison of Serialization Methods

Key Rules

• For binary serialization, classes must be marked with [Serializable] attribute.

• Fields marked with [NonSerialized] are excluded from serialization.

• JSON serialization works with public properties by default.

• Always close file streams after serialization/deserialization operations.

Conclusion

Object serialization in C# converts objects to byte streams for storage or transmission. Binary serialization preserves complete object state but is platform-specific, while JSON serialization offers cross-platform compatibility and human readability. Choose the appropriate method based on your application's requirements for performance, compatibility, and data format.