C# Work with JSON
Learn JSON serialization and deserialization in C#
📦 Working with JSON in C#
JSON (JavaScript Object Notation) is a lightweight data format. C# provides System.Text.Json and Newtonsoft.Json libraries to easily convert objects to JSON strings (serialize) and JSON strings back to objects (deserialize).
// Simple JSON serialization
using System.Text.Json;
var person = new { Name = "John", Age = 30 };
string json = JsonSerializer.Serialize(person);
Console.WriteLine(json);
Output:
{"Name":"John","Age":30}
Understanding JSON in C#
JSON is essential for modern applications, especially web APIs and data exchange. C# makes JSON handling simple with built-in serialization. You can convert C# objects to JSON format for storage or transmission, and parse JSON data back into strongly-typed objects for easy manipulation in your code.
Serialize
Convert object to JSON
string json =
JsonSerializer.Serialize(obj);Deserialize
Convert JSON to object
var obj = JsonSerializer
.Deserialize<Person>(json);Read from File
Load JSON from file
string json =
File.ReadAllText("data.json");
var obj = JsonSerializer
.Deserialize<T>(json);Write to File
Save JSON to file
string json =
JsonSerializer.Serialize(obj);
File.WriteAllText("data.json", json);🔹 Serialize Object to JSON
Serializing a C# object to JSON converts its data into a lightweight, text-based format for storage or transmission. Use Newtonsoft.Json (Json.NET) or System.Text.Json: call JsonConvert.SerializeObject(yourObject) to produce a JSON string. Customize with attributes like [JsonProperty] for naming. JSON is widely used in APIs and web services due to its readability and compatibility with JavaScript and other languages.
using System;
using System.Text.Json;
class Person
{
public string Name { get; set; }
public int Age { get; set; }
public string City { get; set; }
}
class Program
{
static void Main()
{
// Create object
Person person = new Person
{
Name = "John Doe",
Age = 30,
City = "New York"
};
// Serialize to JSON
string json = JsonSerializer.Serialize(person);
Console.WriteLine("Serialized JSON:");
Console.WriteLine(json);
// Pretty print with indentation
var options = new JsonSerializerOptions { WriteIndented = true };
string prettyJson = JsonSerializer.Serialize(person, options);
Console.WriteLine("\nPretty JSON:");
Console.WriteLine(prettyJson);
}
}Output:
Serialized JSON:
{"Name":"John Doe","Age":30,"City":"New York"}
Pretty JSON:
{
"Name": "John Doe",
"Age": 30,
"City": "New York"
}
🔹 Deserialize JSON to Object
Deserializing JSON back to a C# object reconstructs the object from a JSON string, enabling data consumption. Utilize JsonConvert.DeserializeObject<YourType>(jsonString) to map JSON properties to object properties. Ensure your C# class structure matches the JSON schema. Handle exceptions for malformed JSON. This process is essential for reading API responses or configuration files.
using System;
using System.Text.Json;
class Product
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
public bool InStock { get; set; }
}
class Program
{
static void Main()
{
// JSON string
string json = @"{
""Id"": 101,
""Name"": ""Laptop"",
""Price"": 999.99,
""InStock"": true
}";
try
{
// Deserialize JSON to object
Product product = JsonSerializer.Deserialize(json);
Console.WriteLine("Deserialized Object:");
Console.WriteLine($"ID: {product.Id}");
Console.WriteLine($"Name: {product.Name}");
Console.WriteLine($"Price: ${product.Price}");
Console.WriteLine($"In Stock: {product.InStock}");
}
catch (JsonException ex)
{
Console.WriteLine($"JSON Error: {ex.Message}");
}
}
} Output:
Deserialized Object: ID: 101 Name: Laptop Price: $999.99 In Stock: True
🔹 Work with JSON Arrays
Handling JSON arrays in C# involves serializing and deserializing collections like lists or arrays. Serialize a List<T> directly to produce a JSON array. Deserialize a JSON array into a typed collection using List<YourType>. Use LINQ to query or transform the data post-deserialization. This is common when dealing with multiple records from an API or storing sets of structured data.
using System;
using System.Collections.Generic;
using System.Text.Json;
class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int Grade { get; set; }
}
class Program
{
static void Main()
{
// Create list of students
List students = new List
{
new Student { Id = 1, Name = "Alice", Grade = 95 },
new Student { Id = 2, Name = "Bob", Grade = 87 },
new Student { Id = 3, Name = "Charlie", Grade = 92 }
};
// Serialize list to JSON
var options = new JsonSerializerOptions { WriteIndented = true };
string json = JsonSerializer.Serialize(students, options);
Console.WriteLine("JSON Array:");
Console.WriteLine(json);
// Deserialize back to list
List deserializedStudents =
JsonSerializer.Deserialize>(json);
Console.WriteLine("\nDeserialized Students:");
foreach (var student in deserializedStudents)
{
Console.WriteLine($"{student.Name}: {student.Grade}%");
}
}
} Output:
JSON Array:
[
{
"Id": 1,
"Name": "Alice",
"Grade": 95
},
{
"Id": 2,
"Name": "Bob",
"Grade": 87
},
{
"Id": 3,
"Name": "Charlie",
"Grade": 92
}
]
Deserialized Students:
Alice: 95%
Bob: 87%
Charlie: 92%
🔹 Read JSON from File
Reading JSON data from a file in C# loads and parses the content into usable objects. Employ File.ReadAllText(filePath) to get the JSON string, then deserialize as usual. For large files, consider streaming with System.Text.Json.JsonSerializer.DeserializeAsync. Always validate file existence and handle IO exceptions. This method is ideal for configuration, data caches, or local data stores.
using System;
using System.IO;
using System.Text.Json;
class Config
{
public string AppName { get; set; }
public string Version { get; set; }
public int Port { get; set; }
public bool DebugMode { get; set; }
}
class Program
{
static void Main()
{
string filePath = "config.json";
try
{
// Read JSON from file
string json = File.ReadAllText(filePath);
Console.WriteLine("JSON from file:");
Console.WriteLine(json);
// Deserialize to object
Config config = JsonSerializer.Deserialize(json);
Console.WriteLine("\nConfiguration:");
Console.WriteLine($"App Name: {config.AppName}");
Console.WriteLine($"Version: {config.Version}");
Console.WriteLine($"Port: {config.Port}");
Console.WriteLine($"Debug Mode: {config.DebugMode}");
}
catch (FileNotFoundException)
{
Console.WriteLine("Config file not found!");
}
catch (JsonException ex)
{
Console.WriteLine($"Invalid JSON: {ex.Message}");
}
}
} Output:
JSON from file:
{"AppName":"MyApp","Version":"1.0.0","Port":8080,"DebugMode":true}
Configuration:
App Name: MyApp
Version: 1.0.0
Port: 8080
Debug Mode: True
🔹 Write JSON to File
Writing C# objects to a file as JSON persists data in a structured, portable format. Serialize the object to a JSON string, then use File.WriteAllText(filePath, jsonString) to create or overwrite the file. For appending or handling large objects, use StreamWriter. This is useful for saving application state, generating reports, or exporting data for other systems.
using System;
using System.IO;
using System.Text.Json;
using System.Collections.Generic;
class Employee
{
public int Id { get; set; }
public string Name { get; set; }
public string Department { get; set; }
public decimal Salary { get; set; }
}
class Program
{
static void Main()
{
// Create employee data
List employees = new List
{
new Employee { Id = 1, Name = "John", Department = "IT", Salary = 75000 },
new Employee { Id = 2, Name = "Jane", Department = "HR", Salary = 65000 },
new Employee { Id = 3, Name = "Bob", Department = "Sales", Salary = 70000 }
};
string filePath = "employees.json";
try
{
// Serialize with formatting
var options = new JsonSerializerOptions
{
WriteIndented = true
};
string json = JsonSerializer.Serialize(employees, options);
// Write to file
File.WriteAllText(filePath, json);
Console.WriteLine($"✓ Data saved to {filePath}");
Console.WriteLine($"Total employees: {employees.Count}");
Console.WriteLine("\nJSON Content:");
Console.WriteLine(json);
}
catch (Exception ex)
{
Console.WriteLine($"Error: {ex.Message}");
}
}
} Output:
✓ Data saved to employees.json
Total employees: 3
JSON Content:
[
{
"Id": 1,
"Name": "John",
"Department": "IT",
"Salary": 75000
},
{
"Id": 2,
"Name": "Jane",
"Department": "HR",
"Salary": 65000
},
{
"Id": 3,
"Name": "Bob",
"Department": "Sales",
"Salary": 70000
}
]
🔹 Nested JSON Objects
Working with nested JSON objects in C# requires classes that mirror the hierarchical structure. Define child classes or complex properties within your main class. Serialization/deserialization will automatically handle nesting. Use attributes for custom mappings if property names differ. This accommodates complex data models like orders with line items or users with addresses.
using System;
using System.Text.Json;
using System.Collections.Generic;
class Address
{
public string Street { get; set; }
public string City { get; set; }
public string ZipCode { get; set; }
}
class User
{
public int Id { get; set; }
public string Name { get; set; }
public Address Address { get; set; }
public List Hobbies { get; set; }
}
class Program
{
static void Main()
{
// Create nested object
User user = new User
{
Id = 1,
Name = "Alice Johnson",
Address = new Address
{
Street = "123 Main St",
City = "Boston",
ZipCode = "02101"
},
Hobbies = new List { "Reading", "Coding", "Gaming" }
};
// Serialize
var options = new JsonSerializerOptions { WriteIndented = true };
string json = JsonSerializer.Serialize(user, options);
Console.WriteLine("Nested JSON:");
Console.WriteLine(json);
// Deserialize
User deserializedUser = JsonSerializer.Deserialize(json);
Console.WriteLine("\nAccessing nested data:");
Console.WriteLine($"Name: {deserializedUser.Name}");
Console.WriteLine($"City: {deserializedUser.Address.City}");
Console.WriteLine($"Hobbies: {string.Join(", ", deserializedUser.Hobbies)}");
}
} Output:
Nested JSON:
{
"Id": 1,
"Name": "Alice Johnson",
"Address": {
"Street": "123 Main St",
"City": "Boston",
"ZipCode": "02101"
},
"Hobbies": [
"Reading",
"Coding",
"Gaming"
]
}
Accessing nested data:
Name: Alice Johnson
City: Boston
Hobbies: Reading, Coding, Gaming