c# - Net Core API: Make ProducesResponseType Global Parameter or Automate

Question

We have 100+ APIs and have to write ProducesResponseType for all our APIS at the top, 200, 500, etc. Is there a method to make this global parameter for all our get functions, so we don't have to continue repeating code? Trying to make APIs follow Dry principle and be thin controllers.

[HttpGet("[Action]/{id}")]
[ProducesResponseType(typeof(GetBookResponse), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
[ProducesResponseType(typeof(GetBookResponse), StatusCodes.Status500InternalServerError)]
public async Task<ActionResult<GetBookResponse>> GetByBook(int id)
{
   var book = await bookservice.GetBookById(id);
   return Ok(book);
}

Resources:

Set one ProducesResponseType typeof for several HttpStatusCodes

Net Core API: Purpose of ProducesResponseType

Answer 1

You can create a custom IApplicationModelProvider and add the filters you need in OnProvidersExecuting method.

ProduceResponseTypeModelProvider.cs

public class ProduceResponseTypeModelProvider : IApplicationModelProvider
{
    public int Order => 3;

    public void OnProvidersExecuted(ApplicationModelProviderContext context)
    {
    }

    public void OnProvidersExecuting(ApplicationModelProviderContext context)
    {
        foreach (ControllerModel controller in context.Result.Controllers)
        {
            foreach (ActionModel action in controller.Actions)
            {
                // I assume that all you actions type are Task<ActionResult<ReturnType>>

                Type returnType = action.ActionMethod.ReturnType.GenericTypeArguments[0].GetGenericArguments()[0];

                action.Filters.Add(new ProducesResponseTypeAttribute(StatusCodes.Status510NotExtended));
                action.Filters.Add(new ProducesResponseTypeAttribute(returnType, StatusCodes.Status200OK));
                action.Filters.Add(new ProducesResponseTypeAttribute(returnType, StatusCodes.Status500InternalServerError));
            }
        }
    }
}

Then you need to register it to IServiceCollection

Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    ...   
    services.TryAddEnumerable(ServiceDescriptor.Transient<IApplicationModelProvider, ProduceResponseTypeModelProvider>());
    ...
}