How do you read and write JSON data to a file in C#?

Question

Utpal Vishwas · Answer

To read and write JSON data to a file in C#, you typically use the
System.Text.Json namespace (built-in since .NET Core 3.0+). You can also use
Newtonsoft.Json if you prefer, but here's how to do it using the built-in approach:
1. Define a C# Model
public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}
2. Write JSON to a File
using System.Text.Json;
using System.IO;
var person = new Person { Name = "Alice", Age = 30 };
string jsonString = JsonSerializer.Serialize(person, new JsonSerializerOptions { WriteIndented = true });
File.WriteAllText("person.json", jsonString);  // Writes to file
3. Read JSON from a File
string jsonFromFile = File.ReadAllText("person.json");
Person personFromFile = JsonSerializer.Deserializeandlt;Personandgt;(jsonFromFile);
Console.WriteLine($"{personFromFile.Name} is {personFromFile.Age} years old.");
Notes:
JsonSerializer.Serialize(object) converts a C# object to JSON.JsonSerializer.Deserializeandlt;Tandgt;(json) parses JSON into a C# object.The optional WriteIndented = true makes the JSON more readable.
Using Newtonsoft.Json (if preferred):
dotnet add package Newtonsoft.Json
Example:
using Newtonsoft.Json;
var person = new Person { Name = "Bob", Age = 25 };
File.WriteAllText("person.json", JsonConvert.SerializeObject(person, Formatting.Indented));
string json = File.ReadAllText("person.json");
Person loaded = JsonConvert.DeserializeObjectandlt;Personandgt;(json);
Summary
Task
Built-in API
Newtonsoft.Json Equivalent
Serialize to file
JsonSerializer.Serialize
JsonConvert.SerializeObject
Deserialize from file
JsonSerializer.Deserialize
JsonConvert.DeserializeObject

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How do you read and write JSON data to a file in C#?

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1 Answers

1. Define a C# Model

2. Write JSON to a File

3. Read JSON from a File

Notes:

Using `Newtonsoft.Json` (if preferred):

Example:

Summary

Liked By

Task	Built-in API	Newtonsoft.Json Equivalent
Serialize to file	`JsonSerializer.Serialize`	`JsonConvert.SerializeObject`
Deserialize from file	`JsonSerializer.Deserialize`	`JsonConvert.DeserializeObject`