Configuring source-generated JSON serialization in C#:

[JsonSerializable(typeof(UserDto))]
[JsonSerializable(typeof(List<OrderDto>))]
public partial class AppJsonSerializerContext : JsonSerializerContext {}

// Usage
string json = JsonSerializer.Serialize(userDto, AppJsonSerializerContext.Default.UserDto);

Benefits:

• Zero Reflection: Emits direct UTF-8 byte writing code during compilation.
• Zero JIT Startup Delay: Ideal for serverless cold starts.
• Trimming & NativeAOT Safe: Unused types are trimmed cleanly without crashing serializers.

Source generated System.Text.Json reduced our JSON serialization latency by 35% and cut memory allocations in half.

Essential configuration for any ASP.NET Core Minimal API targeting NativeAOT.