在属性中使用类型参数以使用带有泛型类型参数的ProducesResponseType的解决方法？

Question

I have a generic ASP.NET Core WebApi controller like:

public abstract class EntityController<TEntity> 
{
    public IActionResult Get(string id)
    {
        var entity = ... //load from database by id
        if (entity != null) 
            return new JsonResult(value, this.SerializerSettings()) {StatusCode  200};
        return NotFound();
    }
}

and I want to apply following attributes on the Get() method:

[ProducesResponseType(typeof(TEntity), 200)] //this causes compilation error.
[ProducesResponseType(typeof(Object), 404)]

For now, the only work around is to override each method in derived controller and add attributes there:

public class DerivedController ：EntityController<MyEntity>
{
    [ProducesResponseType(typeof(TEntity), (int) HttpStatusCode.OK)]
    [ProducesResponseType(typeof(Object), (int) HttpStatusCode.NotFound)]
    public IActionResult Get(string id)
    {
        return base.Get(id);
    }
}

Ihis is very inconvenient that I should override every REST methods in every controller, just for use the concrete TEntity type in attributes. :-(

Any better work arounds?

Answer 1

Althrough I found no way to use generic type parameter in ProducesResponseTypeAttribute , I found another way to make swagger work:

Use IApplicationModelConvention to update ApplicationModel , which is used by swagger.

public class EntityControllerConversion : IApplicationModelConvention
{
    public void Apply(ApplicationModel application)
    {
        ActionModel action = ... // finds the controller action 
        Type viewModelType = ... // get the view type by reflection from the controller
        SetResponseUsingHack(action, viewModelType, HttpStatusCode.OK);
    }

    private void SetResponseUsingHack(ActionModel actionModel, Type responseType, HttpStatusCode statusCode)
    {
        if (actionModel == null) throw new ArgumentNullException(nameof(actionModel));
        if (responseType == null) throw new ArgumentNullException(nameof(responseType));

        var writable = (IList<object>)(actionModel.Attributes);
        var attribute = FindResponseAttributeUsingHack(writable, statusCode);
        if (attribute != null)
        {
            attribute.Type = responseType;
        }
    }

    private ProducesResponseTypeAttribute FindResponseAttributeUsingHack(IList<object> attributes, HttpStatusCode statusCode)
    {
        if (attributes == null) return null;
        var result = attributes.OfType<ProducesResponseTypeAttribute>()
            .Where(x => x.Type == typeof(ProducesResponseStub))
            .FirstOrDefault(x => x.StatusCode == (int) statusCode);
        return result;
    }
}

public abstract class EntityController<TEntity> 
{
    [HttpGet]
    [ProducesResponseType(typeof(ProducesResponseStub), 200)]
    public IActionResult Get(string id)
    {
    }
}

public static class ProducesResponseStub
{
}

NOTE: Swagger won't work correctly if you just add a new ProducesResponseTypeAttribute instance to ActionModel.Attributes , may be it's a bug in swagger or in asp.net core. That why I use ProducesResponseStub in decorating action methods in EntityController and replace them with correct types in EntityControllerConversion .

Answer 2

从.NET Core 2.1开始，而不是使用IActionResult，你可以使用ActionResult作为返回类型（或任务>），然后swagger也会知道200个调用的返回类型！

Answer 3

The DefaultApiDescriptionProvider in package Microsoft.AspNetCore.Mvc.ApiExplorer has been improved so that it will pick up method return type.

Note that the [ProducesResponseType(StatusCodes.Status200OK)] attribute is required when other [ProducesResponseType] attributes are specified as shown below:

    [HttpGet, Route("")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status400BadRequest, Type = typeof(ProblemDetailsResponse))]
    [ProducesResponseType(StatusCodes.Status404NotFound, Type = typeof(ProblemDetailsResponse))]
    public async Task<IEnumerable<TResponse>> GetAll(int imoNo)
    {
        var parameters = await _parameterService.GetAllAsync(imoNo);

        return parameters.Select(x => MapToResponse(x));
    }

Confirmed to work in Microsoft.AspNetCore.Mvc.ApiExplorer v2.2.0.

Also work with StatusCodes.Status201Created.