9.2 JSON Serialisation and Deserialisation

Let’s go through JSON serialization and deserialization in C# — a common way to convert objects to JSON strings and vice versa.

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📌 1. What is JSON Serialization?

• Serialization converts a C# object into a JSON string.

• Useful for storing, transmitting, or exchanging data between applications.

📌 2. What is JSON Deserialization?

• Deserialization converts a JSON string back into a C# object.

• Makes it easy to read data from APIs, files, or databases.

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📌 3. Using System.Text.Json (Modern Way)

• Available in .NET Core 3.0+ / .NET 5+

• Namespace: System.Text.Json

• Classes: JsonSerializer

Example Class

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

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📌 4. Serialization Example

using System.Text.Json;
 
Person person = new Person { Name = "Alice", Age = 25 };
string jsonString = JsonSerializer.Serialize(person);
Console.WriteLine(jsonString);

Output:

{"Name":"Alice","Age":25}

• Converts the object into JSON string

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📌 5. Deserialization Example

string jsonString = "{\"Name\":\"Bob\",\"Age\":30}";
Person person = JsonSerializer.Deserialize<Person>(jsonString);
Console.WriteLine($"{person.Name} is {person.Age} years old.");

Output:

Bob is 30 years old.

• Converts JSON string back into a C# object

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📌 6. Serialization Options

var options = new JsonSerializerOptions
{
    WriteIndented = true, // Makes JSON readable with line breaks
};
 
string prettyJson = JsonSerializer.Serialize(person, options);
Console.WriteLine(prettyJson);

Output:

{
  "Name": "Alice",
  "Age": 25
}

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📌 7. Using Newtonsoft.Json (Popular Alternative)

• Install NuGet package: Newtonsoft.Json

• Namespace: Newtonsoft.Json

using Newtonsoft.Json;
 
Person person = new Person { Name = "Charlie", Age = 22 };
 
// Serialize
string json = JsonConvert.SerializeObject(person);
 
// Deserialize
Person p = JsonConvert.DeserializeObject<Person>(json);

• More feature-rich, supports advanced scenarios

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📌 8. Working with Collections

List<Person> people = new List<Person>
{
    new Person { Name = "Alice", Age = 25 },
    new Person { Name = "Bob", Age = 30 }
};
 
string json = JsonSerializer.Serialize(people);
var deserializedPeople = JsonSerializer.Deserialize<List<Person>>(json);

• Works with arrays, lists, dictionaries as well

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📌 9. Summary Table

Feature	Description
Serialization	Object → JSON string
Deserialization	JSON string → Object
System.Text.Json	Modern, built-in
Newtonsoft.Json	Feature-rich, widely used
Collections	Supports arrays, lists, dictionaries
Options	Formatting (WriteIndented), ignoring nulls, etc.

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✅ Tip:

• Use System.Text.Json for modern .NET applications

• Use Newtonsoft.Json if you need advanced features like polymorphic serialization, flexible converters, or legacy support