An action method in ASP.NET Core MVC can return many kinds of outcomes, which are referred to as Action outcomes. What kind of response the controller delivers back to the client is determined by these outcomes. The standard technique for returning results from a controller action method is defined by the IActionResult interface. Let's examine the many kinds of results.

1. ViewResult
This result is used to render a view (HTML page) to the client. It is the most common type used in MVC applications.

Example
public IActionResult Index()
{
    return View();
}

2. JsonResult
This result is used to return JSON-formatted data. It is commonly used for API responses.

Example
public JsonResult GetJsonData()
{
    var data = new { Name = "John", Age = 30 };
    return Json(data);
}

3. ContentResult
This result is used to return plain text or any other content.

Example
public ContentResult GetContent()
{
    return Content("Hello, this is plain text.");
}

4. FileResult
This result is used to return a file to the client, such as a document, image, or any other file.

Example
public FileResult GetFile()
{
    var fileBytes = System.IO.File.ReadAllBytes("path/to/file.pdf");
    return File(fileBytes, "application/pdf", "download.pdf");
}

5. RedirectResult
This result is used to redirect the client to a specified URL.

Example
public RedirectResult RedirectToUrl()
{
    return Redirect("https://www.example.com");
}

6. RedirectToActionResult
This result is used to redirect the client to a specific action method in the controller.

Example
public RedirectToActionResult RedirectToActionMethod()
{
    return RedirectToAction("Index", "Home");
}

7. RedirectToRouteResult
This result is used to redirect the client to a specific route.

Example
public RedirectToRouteResult RedirectToRouteMethod()
{
    return RedirectToRoute(new { controller = "Home", action = "Index" });
}

8. StatusCodeResult
This result is used to return a specific HTTP status code.

Example
public StatusCodeResult GetStatusCode()
{
    return StatusCode(404);
}

9. EmptyResult
This result does not return any content.

Example
public EmptyResult DoNothing()
{
    return new EmptyResult();
}

10. PartialViewResult
This result is used to render a partial view.

Example
public PartialViewResult GetPartialView()
{
    return PartialView("_PartialView");
}

11. ObjectResult
This result is used to return an object as the response. It is often used in APIs to return data along with an HTTP status code.

Example
public ObjectResult GetObject()
{
    var data = new { Name = "John", Age = 30 };
    return new ObjectResult(data) { StatusCode = 200 };
}

Conclusion
ASP.NET Core MVC provides a rich set of action results that allow you to return various types of responses from your controller actions. Each result type serves a specific purpose and can be used to meet the requirements of different scenarios. Understanding these result types is crucial for building robust and flexible web applications.

With these action results, you can efficiently manage how your application responds to client requests, whether it's rendering views, returning JSON data, or handling file downloads.