JSON to C# Class Generator

A powerful Python tool that automatically generates strongly-typed C# classes from JSON structures. Perfect for creating DTOs, API models, and data contracts with proper JSON serialization attributes.

Features

✅ Automatic Type Detection - Detects strings, numbers, booleans, dates, arrays, and nested objects
✅ Proper Pluralization - Uses intelligent singularization for array item classes (Activities → Activity)
✅ JsonPropertyName Attributes - Generates proper JSON serialization attributes
✅ Nullable Types - All properties are nullable for robust deserialization
✅ Configurable Namespaces - Customize the generated namespace
✅ Records or Classes - Choose between C# records or traditional classes
✅ Separate Files - Each class generated in its own file for better organization
✅ DateTime Detection - Automatically detects ISO date strings

Installation

1. Clone or download this repository
2. Install dependencies:

   pip install -r requirements.txt

Usage

Basic Usage

# Generate classes from a JSON file
python3 json_to_csharp.py data.json

This will create a Generated/ folder with all the C# class files.

Advanced Usage

# Customize output directory and namespace
python3 json_to_csharp.py data.json \
  --output Models \
  --namespace MyApp.Models \
  --root-class ApiResponse

# Generate records instead of classes
python3 json_to_csharp.py data.json --records

Command Line Options

Option	Short	Default	Description
--output	-o	Generated	Output directory for generated files
--namespace	-n	Generated.Models	C# namespace for generated classes
--root-class	-r	RootDto	Name of the root class
--records		false	Generate records instead of classes
--help	-h		Show help message

Examples

Input JSON

{
  "users": [
    {
      "id": 1,
      "name": "John Doe",
      "email": "john@example.com",
      "createdAt": "2023-01-15T10:30:00Z",
      "isActive": true,
      "profile": {
        "age": 30,
        "city": "New York"
      }
    }
  ],
  "totalCount": 1
}

Generated Output

RootDto.cs

using System.Text.Json.Serialization;
using System;
using System.Collections.Generic;

namespace Generated.Models;

public class RootDto
{
    [JsonPropertyName("users")]
    public List<User>? Users { get; init; }

    [JsonPropertyName("totalCount")]
    public int? TotalCount { get; init; }
}

User.cs

using System.Text.Json.Serialization;
using System;
using System.Collections.Generic;

namespace Generated.Models;

public class User
{
    [JsonPropertyName("id")]
    public int? Id { get; init; }

    [JsonPropertyName("name")]
    public string? Name { get; init; }

    [JsonPropertyName("email")]
    public string? Email { get; init; }

    [JsonPropertyName("createdAt")]
    public DateTime? CreatedAt { get; init; }

    [JsonPropertyName("isActive")]
    public bool? IsActive { get; init; }

    [JsonPropertyName("profile")]
    public Profile? Profile { get; init; }
}

Profile.cs

using System.Text.Json.Serialization;
using System;
using System.Collections.Generic;

namespace Generated.Models;

public class Profile
{
    [JsonPropertyName("age")]
    public int? Age { get; init; }

    [JsonPropertyName("city")]
    public string? City { get; init; }
}

Using Generated Classes

In Your C# Project

using System.Text.Json;
using Generated.Models;

// Deserialize JSON
string jsonString = File.ReadAllText("data.json");
var data = JsonSerializer.Deserialize<RootDto>(jsonString);

// Access strongly-typed properties
var firstUser = data?.Users?.FirstOrDefault();
Console.WriteLine($"User: {firstUser?.Name}, Email: {firstUser?.Email}");
Console.WriteLine($"Age: {firstUser?.Profile?.Age}");

With HttpClient

using System.Net.Http.Json;
using Generated.Models;

var httpClient = new HttpClient();
var response = await httpClient.GetFromJsonAsync<RootDto>("https://api.example.com/data");

foreach (var user in response?.Users ?? [])
{
    Console.WriteLine($"{user.Name} - {user.Email}");
}

Type Mapping

JSON Type	C# Type
string	string?
number (integer)	int?
number (decimal)	decimal?
boolean	bool?
null	object?
array	List<T>?
object	CustomClass?
ISO date string	DateTime?

Smart Naming Conventions

The generator uses intelligent naming conventions while preserving important suffixes and acronyms:

Property Naming

• Preserve Acronyms: FxLinkResponseID → FxLinkResponseID (keeps ID suffix)
• Preserve Numbers: Level1Split, Level2Split → Level1Split, Level2Split (prevents duplicates)
• Pascal Case: user_name → UserName, myProperty → MyProperty

Class Naming

• Pluralization: activities → Activity class (intelligent singularization for arrays)
• Preserve Original Names: Class names maintain their original structure and suffixes

Code Generation Features

• Nullable Context: All files include #nullable enable directive for proper nullable reference types
• Auto-Generated Headers: Each file includes attribution comments
• Consistent Formatting: Clean, readable C# code with proper indentation

Requirements

• Python 3.8+
• inflect library (for proper pluralization)

Testing

The project includes comprehensive tests to ensure reliability and correctness.

Running Tests Locally

# Quick test run
python run_tests.py

# Or run tests manually
pip install -r requirements.txt
python -m pytest test_json_to_csharp.py -v

Test Coverage

The test suite covers:

• ✅ Type Detection - All JSON to C# type conversions
• ✅ Pluralization - Proper singular/plural handling (Activities → Activity)
• ✅ Naming Conventions - PascalCase, DD suffix, str prefix handling
• ✅ File Generation - Actual C# file creation and content verification
• ✅ Nested Objects - Complex object hierarchies
• ✅ Arrays - List handling and item class generation
• ✅ CLI Interface - Command line argument processing
• ✅ Error Handling - Invalid JSON, missing files, etc.
• ✅ Integration Tests - End-to-end workflow testing

Continuous Integration

The project uses GitHub Actions for automated testing:

• Multi-platform: Tests run on Ubuntu, Windows, and macOS
• Multi-version: Python 3.8, 3.9, 3.10, 3.11, and 3.12

All tests must pass before code can be merged.

Contributing

Feel free to submit issues, feature requests, or pull requests to improve this tool!

License

This project is open source. Feel free to use and modify as needed.