public class JsonController : Controller
{
    public class ResultObject
    {
        public int resultCode;
        public string message;
        public bool success;
        public DateTime actionTime;
    }

    public JSONActionResult Run()
    {
        return new JSONActionResult(new ResultObject
                                        {
                                            actionTime = DateTime.Now, 
                                            message = "A message", 
                                            resultCode = 114, 
                                            success = true
                                        });
    }
}

Response:

{"value":{"resultCode":114,"message":"A message","success":true,"actionTime":new Date(1246972828600)}}

RedirectActionResult

Redirects the client to a new URL. Set permanent = true for a HTTP 301 (Moved Permanently) status code.

Example without permanent redirection:

[Url("oldpage/pageId")]
public class PageRedirectController : Controller
{
    public RedirectActionResult Run(string pageId)
    {
        return new RedirectActionResult("/newpage/" + pageId);
    }
}

Response:

...
HTTP/1.x 302 Found
...
Location: /newpage/some_page_id
...

Example with permanent redirection:

[Url("oldpage/pageId")]
public class PageRedirectController : Controller
{
    public RedirectActionResult Run(string pageId)
    {
        return new RedirectActionResult("/newpage/" + pageId, true);
    }
}

Response:

...
HTTP/1.x 301 Moved Permanently
...
Location: /newpage/some_page_id
...

RenderViewActionResult

Default ActionResult for controllers.

Example as you normally would use a controller:

[Url("somepage")]
[View("someview")]
public class RenderViewController : Controller
{
    public void Run()
    {
        // ... do some logic and set some ViewData
    }
}

Example specifically defining the return type and passing the "View" property to the RenderViewActionResult constructor:

[Url("somepage")]
[View("someview")]
public class RenderViewController : Controller
{
    public RenderViewActionResult Run()
    {
        // ... do some logic and set some ViewData
        return new RenderViewActionResult(this.View);
    }
}

Example specifically defining the return type, but returning null. This will cause the default view (someview) to be rendered:

[Url("somepage")]
[View("someview")]
public class RenderViewController : Controller
{
    public RenderViewActionResult Run()
    {
        // ... do some logic and set some ViewData
        return null;
    }
}

SendFileActionResult

Returns a file and sets the specified content type.

Example:

[Url("somepage/file")]
public class SendFileController : Controller
{
    public SendFileActionResult Run(string file)
    {
        byte[] fileBytes = SomeFileHelper.GetFileBytes(file);

        return new SendFileActionResult(fileBytes, "application/octet-stream");
    }
}

StatusCodeActionResult

Returns a HTTP status code response with an optional message.

Example:

[Url("error/{statusCode}")]
public class StatusCodeController : Controller
{
    public StatusCodeActionResult Run(int statusCode)
    {
        string message = "Some default message";
        
        // ... some logic to check the passed status code and set a message

        return new StatusCodeActionResult(statusCode, message);
    }
}

Response (from a call to /error/403) could be:

...
HTTP/1.x 403 Forbidden
...

NotFoundActionResult

Returns the HTTP 404 (Not Found) status code.

NotModifiedActionResult

Returns the HTTP 304 (Not Modified) status code.

Example:

[Url("error/{statusCode}")]
public class StatusCodeController : Controller
{
    public StatusCodeActionResult Run(int statusCode)
    {
        string message = "Some default message";
        
        switch (statusCode)
        {
            case 304:
                return new NotModifiedActionResult();
            case 404:
                return new NotFoundActionResult();
            default:
                return new StatusCodeActionResult(statusCode, message);
        }
    }
}

XmlActionResult

Returns an XML response with content type text/xml.

Example:

[Url("xml")]
public class XmlController : Controller
{
    public XmlActionResult Run()
    {
        string xml = SomeHelper.GenerateXml();
        
        return new XmlActionResult(xml);
    }
}

Response could be something like this:

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
   </book>
   <book id="bk102">
      <author>Ralls, Kim</author>
      <title>Midnight Rain</title>
   </book>
   <book id="bk103">
      <author>Corets, Eva</author>
      <title>Maeve Ascendant</title>
   </book>
   <book id="bk104">
      <author>Corets, Eva</author>
      <title>Oberon's Legacy</title>
   </book>
   <book id="bk105">
      <author>Corets, Eva</author>
      <title>The Sundered Grail</title>
   </book>
</catalog>