JsonSerializerContext not working with minimalApi

[dany28]

I've tried to switch with my microservice to Net8 Minimal API, for startup time and performance reason I've decided to use JsonSerializerContext, but I cannot achieve work solution, my simplest code for testing:

using System.Text.Json;
using System.Text.Json.Serialization;

var builder = WebApplication.CreateSlimBuilder(args);

builder.Services.ConfigureHttpJsonOptions(options =>
    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default));

var app = builder.Build();

app.MapGet("/json", () => new Person("Alex"));
app.MapGet("/string", () => JsonSerializer.Serialize(new Person("Alex"),AppJsonSerializerContext.Default.Person));

app.Run();

record Person(string FirstName)
{
}

[JsonSerializable(typeof(Person))]
internal partial class AppJsonSerializerContext : JsonSerializerContext
{

}

endpoint /string with manual serialization of course return (original field names):

{"FirstName":"Alex"}

but /json returns result like normal serialization (camelCase field names):

{
  "firstName": "Alex"
}

JsonSerializerContext not working at endpoint /json, resulted JSON should be the same like in /string end point

project configuration is default:

<Project Sdk="Microsoft.NET.Sdk.Web">

    <PropertyGroup>
        <TargetFramework>net8.0</TargetFramework>
        <Nullable>enable</Nullable>
        <ImplicitUsings>enable</ImplicitUsings>
        <InvariantGlobalization>true</InvariantGlobalization>
    </PropertyGroup>

    <ItemGroup>
        <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.0"/>
    </ItemGroup>

</Project>

[martincostello]

Try making this change:

  [JsonSerializable(typeof(Person))]
+ [JsonSourceGenerationOptions(PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase)]
  internal partial class AppJsonSerializerContext : JsonSerializerContext
  {
  }

(It wasn't clear to me which one was the one you expected, so I've edited this from Unspecified to CamelCase - if you wanted the opposite, then switch the value for the other)

[dany28]

I understand why with my configuration I've received FirstName with manual using JsonSerializerContext at endpoint /string, generated source contains original field names.

My question is: Why endpoint /json is not using AppJsonSerializerContext ? This line should enable it for every endpoint:

builder.Services.ConfigureHttpJsonOptions(options =>
    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default));

[martincostello]

Closing as this has been moved to #52088.