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JSON to C# Class

Paste a JSON object or API response and get C# model classes or records with PascalCase properties, the right numeric and nullable types, and optional System.Text.Json or Newtonsoft.Json attributes. Conversion runs entirely in your browser.

Root class name

Namespace (optional)

Declare as

JSON attributes

Collections

Decimal numbers

Nullable reference types (string?) DateTime for date strings Live update

JSON input

Open .json

C# code

Your JSON is parsed locally in this tab and never uploaded. Tip: Ctrl + Enter generates.

How to use the JSON to C# Class

Paste your JSON into the left box, or open a .json file. A sample is loaded so you see output right away.
Name the root class and set a namespace, or clear it to leave the namespace out.
Choose the options: class or record, attribute library, collection type, double or decimal, nullable reference types and DateTime detection.
Press Generate C# Classes. With Live update on, the code updates as you type.
Copy or download the .cs file and deserialize with JsonSerializer.Deserialize<Root>(json).

Example: JSON to a C# class

For {"id": 7, "user_name": "ada", "price": 9.99, "tags": ["new"], "shippedAt": null} the default options (System.Text.Json, nullable reference types) produce:

public class Root
{
    [JsonPropertyName("id")]
    public int Id { get; set; }

    [JsonPropertyName("user_name")]
    public string UserName { get; set; } = string.Empty;

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

    [JsonPropertyName("tags")]
    public List<string> Tags { get; set; } = new();

    [JsonPropertyName("shippedAt")]
    public object? ShippedAt { get; set; }
}

Deserialize it with var root = JsonSerializer.Deserialize<Root>(json); (System.Text.Json) or JsonConvert.DeserializeObject<Root>(json) (Newtonsoft.Json).

How JSON values map to C# types

JSON value	C# type
`"text"`	`string` (`string?` if it can be null or missing)
`"2024-05-01T09:30:00Z"`	`DateTime` (when date detection is on)
`42`	`int`; `long` above 2,147,483,647
`9.99`	`double` or `decimal`
`true`	`bool` (`bool?` if it can be null or missing)
`{ … }`	A separate class or record
`{}`	`Dictionary<string, object?>`
`["a"]`	`List<string>`, `string[]` or `IReadOnlyList<string>`
`[]`, mixed values, always null	`object` / `List<object>`

Tips for clean C# models

Use decimal for money. double cannot represent 0.1 exactly, so prices and balances should be decimal.
Case-insensitive matching. Without attributes, System.Text.Json matches property names case-sensitively unless you set PropertyNameCaseInsensitive = true or use JsonSerializerDefaults.Web. The generated attributes avoid that problem entirely.
Prefer DateTimeOffset for zoned times. If timestamps carry an offset like +02:00 and you need to keep it, change DateTime to DateTimeOffset.
Use real samples. Paste an array with several items so the generator can see which properties are optional or nullable.

Frequently asked questions

System.Text.Json or Newtonsoft.Json attributes?

System.Text.Json is built into .NET Core 3.0 and later and is the default in ASP.NET Core, so [JsonPropertyName("…")] is the usual choice. Pick Newtonsoft.Json if your project already uses Json.NET; it gets [JsonProperty("…")]. The attributes map each PascalCase property back to the exact JSON key, so deserialization works regardless of naming policy.

Class or record?

Records (C# 9 and later) give you value-based equality and with-expressions, and the generated init accessors make objects immutable after creation, which suits DTOs and API responses. Classes with get; set; are mutable and work with every C# version and serializer.

How are numbers typed?

Whole numbers become int, or long when any value is outside the 32-bit range. Numbers with a decimal point or exponent become double, or decimal if you choose it, which is better for money. A field that mixes whole and decimal numbers uses the decimal type you selected.

How are null and missing values handled?

Value types that are null or missing in some items become nullable, such as int? or bool?. With nullable reference types on, nullable strings, lists and classes get a ?, and non-nullable ones are initialised (string.Empty, new()) so the compiler does not warn. The file starts with #nullable enable for that reason.

How are property names created?

Keys are split into words at underscores, dashes, spaces and camelCase boundaries and joined in PascalCase, so avatar_url becomes AvatarUrl and email-notifications becomes EmailNotifications. A key that would match the class name gets a Value suffix, because C# does not allow a member with the same name as its type.

What does an array or mixed value become?

An array of objects becomes a List of one class merged from all items. An empty array becomes List<object>, and values that mix types (for example numbers and strings) become object, because C# has no union types.

Is my JSON uploaded?

No. Everything happens in JavaScript in this page, so your JSON never leaves your device.

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