JSON to C# Converter

Convert JSON to C# Online

Use our free json to csharp converter to generate well-structured C# class definitions from any JSON data instantly. Whether you are building json to c# models for ASP.NET Core APIs, creating data transfer objects for Blazor applications, or scaffolding entity classes for .NET microservices, this tool produces clean, compilable C# code from your JSON input without any installation required.

What is JSON Format

JSON, short for JavaScript Object Notation, is a lightweight data interchange format that serves as the universal standard for web-based data communication. Its syntax of key-value pairs enclosed in curly braces and ordered arrays enclosed in square brackets makes it intuitive for both humans and machines. JSON supports strings, numbers, booleans, null, nested objects, and arrays as value types.

JSON has become the default format for REST API responses, NoSQL database storage, configuration files, and data exchange between microservices. The .NET ecosystem provides excellent JSON support through System.Text.Json and the popular Newtonsoft.Json library, both of which handle serialization and deserialization between JSON strings and C# objects seamlessly. This makes JSON the primary data format for ASP.NET Core web APIs and .NET client applications.

What is C# Class Format

C# classes are the fundamental building blocks of .NET applications, defining the structure and behavior of objects through properties, constructors, and methods. In modern C# development, classes used for data transfer typically use auto-implemented properties with get and set accessors, providing a clean and concise syntax for defining data shapes. These classes serve as data transfer objects, view models, entity models, and configuration holders throughout .NET applications.

C# enforces strong typing with a rich type system that includes value types like int, double, and bool, reference types like string and custom classes, nullable types using the question mark syntax, and generic collections like List and Dictionary. Modern C# features like records, init-only setters, and nullable reference types provide additional tools for defining immutable and null-safe data models. The language supports attributes for controlling serialization behavior, with JsonPropertyName from System.Text.Json and JsonProperty from Newtonsoft.Json being the most commonly used for JSON mapping.

How the Conversion Works

Converting JSON to C# involves analyzing the structure and values of a JSON document to infer appropriate C# types for each property. The converter parses the input JSON, examines each value to determine its C# type, and generates class definitions with auto-implemented properties. Strings become string, integers become int, floating-point numbers become double, booleans become bool, null values become nullable types, arrays become List collections, and nested objects become separate named classes.

The conversion engine follows C# naming conventions by converting JSON keys to PascalCase property names. If your data originates in another format, you can first convert XML to JSON before generating C# classes. For working with your JSON data in other ways, try our JSON to XML converter for legacy .NET XML integration, or explore the JSON to TypeScript converter for Blazor WebAssembly frontend type definitions. You can also generate Java classes if your project spans both JVM and .NET ecosystems.

Syntax Comparison

The mapping between JSON data and C# classes is clean and well-defined. A JSON object like this:

// JSON
{
  "name": "Alice",
  "age": 30,
  "active": true,
  "score": 95.5
}

Generates the following C# class:

// C#
public class Root
{
    public string Name { get; set; }
    public int Age { get; set; }
    public bool Active { get; set; }
    public double Score { get; set; }
}

JSON arrays are mapped to C# List collections with appropriate generic type parameters. A JSON array of strings becomes List<string>, while an array of objects generates a separate class and uses List<ChildClass> as the property type. Nested JSON objects produce additional named classes referenced as property types in the parent class. The converter uses JsonPropertyName attributes when the JSON key differs from the PascalCase property name to ensure correct serialization mapping.

Common Use Cases

The most common use case for JSON to C# conversion is creating data transfer objects for ASP.NET Core Web API projects. Developers consuming external REST APIs need C# classes that match the JSON response structure for deserialization with System.Text.Json or Newtonsoft.Json. Rather than manually writing these classes from API documentation, developers can paste a sample response and instantly generate the required class hierarchy.

Another frequent scenario involves Blazor application development, where JSON responses from backend services need to be deserialized into C# objects for rendering in the UI. Entity Framework Core developers also use this conversion to quickly scaffold entity classes when reverse-engineering JSON data exports from existing databases. Azure Functions and other serverless .NET applications that process JSON messages from queues, event hubs, or HTTP triggers benefit from having accurately typed C# models generated from sample payloads.

JSON to C# Examples

The following examples demonstrate how various JSON structures are converted into C# class definitions. These cover the most common patterns encountered when generating typed models from API responses and data sources.

A JSON object with nested structures generates multiple related classes:

// JSON Input
{
  "order": {
    "id": "ORD-2024-001",
    "customer": {
      "name": "Alice Johnson",
      "email": "alice@example.com"
    },
    "items": [
      {"product": "Widget", "quantity": 3, "price": 9.99},
      {"product": "Gadget", "quantity": 1, "price": 24.99}
    ],
    "total": 54.96,
    "shipped": false
  }
}

// C# Output
public class Customer
{
    public string Name { get; set; }
    public string Email { get; set; }
}

public class Item
{
    public string Product { get; set; }
    public int Quantity { get; set; }
    public double Price { get; set; }
}

public class Order
{
    public string Id { get; set; }
    public Customer Customer { get; set; }
    public List<Item> Items { get; set; }
    public double Total { get; set; }
    public bool Shipped { get; set; }
}

Frequently Asked Questions

Does the converter support System.Text.Json or Newtonsoft.Json?

The converter generates plain C# classes with auto-implemented properties that are compatible with both System.Text.Json and Newtonsoft.Json out of the box. When JSON keys use camelCase or snake_case naming that differs from the PascalCase C# property names, the converter adds appropriate JsonPropertyName attributes for System.Text.Json compatibility. You can easily swap these for Newtonsoft.Json JsonProperty attributes if your project uses that library instead.

How are JSON null values handled in C#?

JSON null values are represented using C# nullable types. Value type properties that can be null use the nullable syntax like int? or double?. Reference type properties like string are marked as nullable with string? when nullable reference types are enabled. This ensures the generated classes accurately represent which fields may contain null values in the JSON data, preventing null reference exceptions at runtime.

Can I use the generated classes with ASP.NET Core?

Yes, the generated C# classes work seamlessly with ASP.NET Core applications. You can use them directly as parameter types in controller action methods with the FromBody attribute, as return types for API responses, or as model classes for Entity Framework Core. ASP.NET Core uses System.Text.Json by default for JSON serialization, and the generated classes follow the conventions that the serializer expects for automatic binding.

Does the tool generate C# records instead of classes?

The converter generates traditional C# classes with mutable properties for maximum compatibility across .NET versions. C# records, introduced in C# 9, provide a more concise syntax for immutable data types with built-in value equality. If your project targets .NET 5 or later and you prefer records, you can refactor the generated class into a record declaration. For simple cases, a class like public class User can become public record User(string Name, int Age).

How are nested JSON objects handled?

Each nested JSON object generates a separate C# class with its own properties. The parent class references the child class as a property type, creating a clean class hierarchy that mirrors the JSON structure. Class names are derived from the JSON key names using PascalCase convention. This modular approach produces maintainable code that follows C# best practices for class organization.

How are JSON arrays represented in C#?

JSON arrays are mapped to List<T> properties with appropriate generic type parameters. An array of strings becomes List<string>, an array of numbers becomes List<int> or List<double>, and an array of objects becomes a List of the generated child class type. The converter includes the necessary using statement for System.Collections.Generic when List types are used in the generated code.

Is the conversion performed securely?

Yes, the entire JSON to C# conversion runs client-side in your browser. No data is transmitted to any external server, ensuring complete privacy and security. This makes the tool safe for converting JSON containing sensitive information such as API responses with user data, Azure configuration files, or proprietary business data. Your input never leaves your browser session and is never stored or logged anywhere.

How does this compare to generating Go or Rust structs?

C# classes are more feature-rich than Go or Rust structs, offering auto-implemented properties, nullable reference types, and rich attribute support. Go structs use struct tags for serialization control, while Rust structs use derive macros. Each language target serves its ecosystem best. For alternatives, explore our JSON to Go struct converter or JSON to Rust struct generator.