IActionResult vs ActionResult<T> in ASP.NET Core

IActionResult vs ActionResult<T> in ASP.NET Core

Example: Using IActionResult

[HttpGet]
public IActionResult GetProduct(int id)
{
    var product = _repo.Find(id);
    if (product == null)
        return NotFound();
    return Ok(product);
}

Example: Using ActionResult<Product>

[HttpGet]
public ActionResult<Product> GetProduct(int id)
{
    var product = _repo.Find(id);
    if (product == null)
        return NotFound();
    return product; // Implicitly wrapped in Ok()
}

When to Use What

• Use IActionResultWhen : Full control over response types, no fixed model.
  • You want full control over HTTP responses.
  • You're returning different types (e.g., FileResult, RedirectResult, etc.).
  • You’re not returning a model directly.
• Use ActionResult when:Cleaner syntax, better Swagger support, model + status code.
  • You want to return a model (T) and still support status codes.
  • You want better Swagger/OpenAPI documentation.
  • You prefer cleaner syntax with implicit Ok() wrapping.

Testing Tip

var result = controller.GetProduct(1);
var okResult = Assert.IsType<OkObjectResult>(result.Result);
var product = Assert.IsType<Product>(okResult.Value);