JSON to CSharp Class

About this tool

Writing C# model classes by hand from JSON responses is slow and easy to get wrong when payloads are nested. The JSON to C# Class Generator parses a JSON sample in your browser and writes System.Text.Json-ready classes. Keys become PascalCase properties, and when the C# name differs from the JSON key a [JsonPropertyName("key")] attribute keeps the wire name. Nested objects become their own classes named after the parent and property (for example RootModelAddress), and arrays become List<T> with the element type taken from the first non-null item; mixed or empty arrays become List<object>. Numbers map to int or double, true and false to bool, strings to string and null to object. The output starts with using lines for System.Collections.Generic and System.Text.Json.Serialization. Set the root class name, click Convert and copy the result. Dates, GUIDs and large integers are not detected, so change those property types by hand where needed.

Why use it

• System.Text.Json Ready: [JsonPropertyName] attributes keep the original snake_case or camelCase keys while properties follow C# PascalCase naming.

• Nested Classes Generated for You: Every nested object gets its own class, named after its parent and property so names stay unique.

• Typed Collections: Arrays become List<T> with the element type inferred from the data, including lists of generated classes.

• Instant Validation: Invalid JSON is reported with the parser's error message before anything is generated.

• Runs Locally: Parsing and code generation happen in your browser; the JSON you paste is not uploaded.

How to use

1. Enter a Root Class Name (RootModel by default).
2. Paste a JSON sample into JSON Input; click Beautify to format it if it is minified.
3. Click Convert to generate the classes, or read the error message if the JSON is invalid.
4. Review the types and change any that need it — for example string to DateTime or Guid, int to long, or double to decimal.
5. Click Copy and paste the classes into your project.

When it helps

• When consuming a new REST API and needing strongly-typed response models quickly
• When a third-party webhook payload arrives and you need C# deserialization classes
• When prototyping a new feature that reads JSON configuration files
• When onboarding onto a legacy codebase that still uses raw JObject instead of typed models
• When writing integration tests and needing matching C# request/response contracts
• When you have a sample JSON response but no schema and need a first draft of the C# model

Examples

{"user_id": 42, "email": "dev@example.com", "created_at": "2024-01-15T09:00:00Z", "address": {"city": "Berlin", "zip": "10115"}}

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

public class RootModelAddress
{
    [JsonPropertyName("city")]
    public string City { get; set; }

    [JsonPropertyName("zip")]
    public string Zip { get; set; }
}

public class RootModel
{
    [JsonPropertyName("user_id")]
    public int UserId { get; set; }

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

    [JsonPropertyName("created_at")]
    public string CreatedAt { get; set; }

    [JsonPropertyName("address")]
    public RootModelAddress Address { get; set; }
}

Root Class Name: Order; JSON: {"order_id": 7, "order_items": [{"sku": "A1", "qty": 2, "price": 9.99}]}

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

public class OrderOrderItem
{
    [JsonPropertyName("sku")]
    public string Sku { get; set; }

    [JsonPropertyName("qty")]
    public int Qty { get; set; }

    [JsonPropertyName("price")]
    public double Price { get; set; }
}

public class Order
{
    [JsonPropertyName("order_id")]
    public int OrderId { get; set; }

    [JsonPropertyName("order_items")]
    public List<OrderOrderItem> OrderItems { get; set; }
}

{"trace_id": "a3f1e2d4-bc09-4c71-8e55-123456789abc", "error": null, "count": 1500000000, "ok": true}

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

public class RootModel
{
    [JsonPropertyName("trace_id")]
    public string TraceId { get; set; }

    [JsonPropertyName("error")]
    public object Error { get; set; }

    [JsonPropertyName("count")]
    public int Count { get; set; }

    [JsonPropertyName("ok")]
    public bool Ok { get; set; }
}

Tips

• Paste a real API response with populated values rather than an empty skeleton so the type inference engine has concrete data to analyze
• After generating, rename RootModel and generated nested class names such as RootModelAddress to meaningful domain names before committing.
• If your JSON uses snake_case keys, the [JsonPropertyName] attribute keeps the original key, so deserialization still works after properties are renamed to PascalCase.
• For financial data, manually change inferred double properties to decimal after generation to avoid floating-point precision issues
• Change properties that hold dates or UUIDs from string to DateTime or Guid after generating — the tool types them as string.

Frequently Asked Questions

Glossary

POCO

Plain Old CLR Object — a simple C# class with no framework inheritance or attributes required. JSON deserialization targets are typically POCOs.

JsonProperty

A Newtonsoft.Json attribute that maps a C# property name to its JSON key, allowing PascalCase properties to serialize to/from camelCase or snake_case wire format.

Nullable Reference Types

A C# 8 feature enabled via <Nullable>enable</Nullable> that distinguishes string (non-null guaranteed) from string? (may be null) at compile time, reducing NullReferenceExceptions.

System.Text.Json

The built-in .NET JSON serializer introduced in .NET Core 3.0, offering better performance than Newtonsoft.Json with a slightly stricter API surface.

Type Inference

The process of determining a variable's or property's data type from its value rather than an explicit annotation — used here to map JSON values to appropriate C# primitive types.

Deserialization

Converting a JSON string into a populated C# object graph, the reverse of serialization. Requires class definitions whose properties match the JSON structure.