How to configure JSON Name Case policy while using MinimalApi

Question

I'm trying to get result from my minimal API who configured in endpoints of my MVC web application my Get action configured like this :

            endpoints.MapGet(
                "HO-CFDZU4/api/Currency/Get", 
                [PermissionAuthorize(PermissionName.ReadCurrencyDictionary)] 
                async ([FromServicesAttribute] CurrencyService curency) =>
            {
                var result = await DataSourceLoader.LoadAsync(curency.Get(), new DataSourceLoadOptions());

                return Results.Ok(result);
            });

As result i get response with object where property names changed to lowercase, and its not suit for me. I want to get exactly same name in same case like i return form action.

To get similar effect in MVC i used this code :

            services
            .AddMvc()
            .AddFluentValidation(x => x.RegisterValidatorsFromAssembly(AppDomain.CurrentDomain.GetAssemblies().Where(x => x.FullName.Contains("ApplicationCore")).Single()))
            .AddMvcLocalization()
            .AddMvcOptions(options =>{})
            .AddRazorRuntimeCompilation()
            .AddJsonOptions(options =>
            {
                options.JsonSerializerOptions.PropertyNamingPolicy = null;
                options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles;
            });

Which setup property naming policy for Json while using action in controllers, and i dont know how to setup same policy for minimalApi.

What Ive tried is to set [JsonPropertyName(name)] And it working good but we have lot of classes and i looking for more global solution.

I also tried configure JsonOptions globally like this:

        services.Configure<JsonOptions>(options =>
        {
            options.JsonSerializerOptions.PropertyNamingPolicy = null;
            options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles;
        });

But it do nothing

Answer 1

Use JsonOptions from Microsoft.AspNetCore.Http.Json namespace (docs):

services.Configure<JsonOptions>(options =>
{
    options.SerializerOptions.PropertyNamingPolicy = null;
    options.SerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles;
});

UPD

If your application uses both Minimal APIs endpoints and MVC ones, then you try to configure options from both namespaces:

services.Configure<Microsoft.AspNetCore.Http.Json.JsonOptions>(options =>
{
    options.SerializerOptions.PropertyNamingPolicy = null;
    options.SerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles;
});
services.Configure<Microsoft.AspNetCore.Mvc.JsonOptions>(options =>
{
    options.JsonSerializerOptions.PropertyNamingPolicy = null;
    options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles;
});

UPD 2

Since .NET 7 you can use HttpJsonServiceExtensions.ConfigureHttpJsonOptions for "Minimal APIs" ones:

builder.Services.ConfigureHttpJsonOptions(opts => opts.SerializerOptions.IncludeFields = true);