.NET Core Web API - Return ActionResult<T> from Actions

ValuesController.cs

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    [HttpPut("{id}")]
    public ActionResult<SubjectSummary> Put([FromRoute] int id, [FromBody] SubjectSummary summary)
    {
        // Hypothetical checks to explain the concept
        if (id < 0)
        {
            return BadRequest();
        }

        // Hypothetical checks to explain the concept
        if (id > 10)
        {
            return NotFound();
        }

        // Implicit Conversion to ActionResult<SubjectSummary>
        return summary;
    }
}