ASP.NET MVC controller actions that return JSON or partial html

In your action method, return Json(object) to return JSON to your page.

public ActionResult SomeActionMethod() {
  return Json(new {foo="bar", baz="Blech"});
}

Then just call the action method using Ajax. You could use one of the helper methods from the ViewPage such as

<%= Ajax.ActionLink("SomeActionMethod", new AjaxOptions {OnSuccess="somemethod"}) %>

SomeMethod would be a javascript method that then evaluates the Json object returned.

If you want to return a plain string, you can just use the ContentResult:

public ActionResult SomeActionMethod() {
    return Content("hello world!");
}

ContentResult by default returns a text/plain as its contentType.
This is overloadable so you can also do:

return Content("<xml>This is poorly formatted xml.</xml>", "text/xml");

Another nice way to deal with JSON data is using the JQuery getJSON function. You can call the

public ActionResult SomeActionMethod(int id) 
{ 
    return Json(new {foo="bar", baz="Blech"});
}

Method from the jquery getJSON method by simply...

$.getJSON("../SomeActionMethod", { id: someId },
    function(data) {
        alert(data.foo);
        alert(data.baz);
    }
);

To answer the other half of the question, you can call:

return PartialView("viewname");

when you want to return partial HTML. You'll just have to find some way to decide whether the request wants JSON or HTML, perhaps based on a URL part/parameter.

You may want to take a look at this very helpful article which covers this very nicely!

Just thought it might help people searching for a good solution to this problem.

http://weblogs.asp.net/rashid/archive/2009/04/15/adaptive-rendering-in-asp-net-mvc.aspx