JSON to C# Model Converter

What is a JSON to C# model converter?

A JSON to C# model converter reads a JSON payload and automatically generates C# POCO (Plain Old CLR Object) classes that match the JSON structure. Instead of reading an API's JSON response and manually writing each property, its type, and its nested classes, the converter produces correct, ready-to-compile C# code in seconds. Nested JSON objects become nested C# classes, arrays become List<T> properties, and JSON types map to the correct C# primitives (string, int, bool, double).

What is a POCO?

POCO stands for Plain Old CLR Object — a simple C# class with only properties and no special base classes or framework dependencies. POCOs are the standard pattern in .NET for representing data: they work with System.Text.Json and Newtonsoft.Json for serialisation, with Entity Framework Core for database mapping, and with HTTP client methods like GetFromJsonAsync<T>(). A generated POCO is a starting point — you add data annotations, validation attributes, or business logic on top as needed.

System.Text.Json vs Newtonsoft.Json

Modern .NET projects (5+) use System.Text.Json by default, which is built into the runtime and has excellent performance. Older .NET Framework projects and many existing codebases use Newtonsoft.Json (Json.NET). The generated models work with both, but the attribute names differ:

• System.Text.Json: [JsonPropertyName("snake_case_field")]
• Newtonsoft.Json: [JsonProperty("snake_case_field")]

Add these attributes to your properties when the JSON field names differ from C# naming conventions — for example when the API returns user_id but you want a property named UserId.

How to use this tool

1. Enter your desired root class name in the class name field.
2. Paste a sample JSON payload into the input editor.
3. Click Convert.
4. Copy the generated C# classes and paste them into your .NET project.
5. Adjust property names, add attributes, or implement interfaces as needed.

Using generated models with HttpClient

Once you have a generated POCO, consuming a JSON API in .NET is straightforward using the System.Net.Http.Json extension methods:

• await httpClient.GetFromJsonAsync<MyModel>(url) — deserialises a GET response directly into your model
• await httpClient.PostAsJsonAsync(url, myModel) — serialises your model and posts it as JSON

These methods handle serialisation, deserialisation, and error checking, so the generated model is all you need to start consuming an API. For more complex scenarios — custom converters, polymorphic types, or handling null values — use JsonSerializerOptions to configure the deserialiser.