In this article
Why Generate C# Classes from JSON?
When working with REST APIs in .NET or Unity, you need strongly-typed C# classes to deserialize JSON responses. Writing these classes by hand is tedious and error-prone, especially for deeply nested API payloads with dozens of properties. A JSON to C# generator analyzes the JSON structure and produces ready-to-use class definitions automatically.
This is particularly valuable during rapid prototyping. You paste a sample API response, get perfectly structured C# classes, and immediately start working with typed data instead of wrestling with dynamic objects or dictionary lookups. The generated code follows C# conventions and includes the correct serialization attributes for your chosen framework.
Output Modes and Serialization Options
The generator supports multiple output formats to match your project's coding style and .NET version. Each mode produces idiomatic C# that compiles without modification.
- Class vs Record — traditional mutable classes for older .NET projects, or C# 9+ records for immutable data transfer objects with built-in value equality
- System.Text.Json — the modern, high-performance serializer built into .NET Core 3.1+ that uses [JsonPropertyName] attributes for property mapping
- Newtonsoft.Json — the widely-used Json.NET library that uses [JsonProperty] attributes, still dominant in legacy .NET Framework and Unity projects
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Convert JSON to C# →C# Naming Conventions and Annotations
C# follows strict naming conventions that differ from JSON's typical camelCase or snake_case. The generator automatically applies these transformations while preserving the original JSON property names through serialization attributes.
- PascalCase properties — all generated property names are converted to PascalCase (e.g., user_name becomes UserName) following Microsoft's .NET naming guidelines
- Annotation patterns — each property includes the appropriate serialization attribute ([JsonPropertyName] or [JsonProperty]) that maps the PascalCase property back to the original JSON key name
- Type inference — the generator infers C# types from JSON values: strings become string, numbers become int or double, booleans become bool, and null values become nullable reference types
Frequently Asked Questions
How does the generator handle nullable reference types?
When a JSON value is null, the generator produces a nullable reference type (string? instead of string). This follows C# 8+ nullable reference type conventions and helps you catch potential null reference exceptions at compile time rather than runtime.
Should I use List<T> or arrays for JSON arrays?
The generator uses List<T> by default because it provides richer functionality (Add, Remove, Contains) and is the most common collection type in C# codebases. If you need arrays for performance-critical scenarios or API contracts that require fixed-size collections, you can manually change the generated type.
Can I generate records instead of classes?
Yes. The record output mode generates C# 9+ record types with init-only properties. Records are ideal for data transfer objects because they provide immutability, value-based equality, and concise syntax with positional parameters. They require .NET 5+ or C# 9+ to compile.