ActionResult<IEnumerable<Model>> vs IActionResult in ASP.NET Core WebAPI

Question

Hello,

What is the difference between ActionResult<IEnumerable<SpeakerModel>> vs IActionResult ?

I ran both of them and got the same result.

       public IActionResult GetAll()
       {
            return Ok(SpeakersList);
       }

          [HttpGet]
          public ActionResult<IEnumerable<SpeakerModel>> GetAll()
          {
               return Ok(SpeakersList);
          }

Answer 1

one is strong typed and will give compile error if return value does not match. also via reflection the return type can be deduced say for swagger.

the other just returns any object.

Answer 2

Hi @Shervan360,

IActionResult type

This solves the problem above as the IActionResult return type covers different return types.

public IActionResult Get() {
    SpeakerModel model= ...;
    if(model== null)
    {
        return NotFound();
    }        
    else
    {
        return Ok(model);
    }
        
}

ActionResult type

ASP.NET Core includes the ActionResult<T> return type for web API controller actions. It enables returning a type deriving from ActionResult or return a specific type. ActionResult<T> offers the following benefits over the IActionResult type:

• The [ProducesResponseType] attribute's Type property can be excluded. For example, [ProducesResponseType(200, Type = typeof(SpeakerModel ))] is simplified to [ProducesResponseType(200)]. The action's expected return type is inferred from the T in ActionResult<T>.
• Implicit cast operators support the conversion of both T and ActionResult to ActionResult<T>. T converts to ObjectResult, which means return new ObjectResult(T); is simplified to return T;.

    public ActionResult<SpeakerModel > Get()
    {
       SpeakerModel model= ...;
        if(model== null){
          return NotFound();
        }
        return model;
    }
  

Reference

Controller action return types in ASP.NET Core web API

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Best regards,
Rena