Returning Json from controller, never a success - asp.net-mvc-3

Question

I'm successfully posting to my controller with the following code, however, success is never being hit only error. What am I doing wrong?
JS:
$.ajax({
url: '/Home/Subscribe',
type: 'POST',
dataType: 'json',
data: { email: $('#sube').val() },
success: function (data) {
// get the result and do some magic with it
alert(data.foo);
},
error: function (XMLHttpRequest, textStatus, errorThrown) {
alert(textStatus);
}
});
Controller:
[HttpPost]
public JsonResult Subscribe(string email)
{
return Json(new { foo = "bar", baz = "Blech" });
}

Answer 1

In IE, press F12 to open developer tools. Go to Network tab and click on Start Profiler. Send a request to your Subscribe action - in a list below you will see details of sent request and returned status code. Double click on request to see details - you can then see body of your response. If the request failed with a server error, you will see that error in a body of your response.

Answer 2

One wrong thing I see with your code is that you have hardcoded the url:
url: '/Home/Subscribe'
You should never do this. You should always use url helpers when generating urls in an ASP.NET MVC application:
url: '#Url.Action("Subscribe", "Home")'
Also you are saying that the error callback is always hit but you didn't say what you observed in FireBug or Chrome Developer toolbar when you tried to analyze the AJAX request. If you had done this you would have seen the exact cause of failure for the request because you would have seen what request is sent to the server and what response does the server sends back to the client.

Answer 3

The following is my jQuery ajax snippet that works. Your controller looks right. I assume you have verified it is actually getting called by using a breakpoint.
var p = {
email: $('#sube').val()
};
$.ajax({
url: '#Url.Action("Subscribe", "Home")'
type: 'POST',
data: JSON.stringify(p),
dataType: "text json",
contentType: "application/json",
success: function (data) {
// get the result and do some magic with it
alert(data.foo);
},
error: function (XMLHttpRequest, textStatus, errorThrown) {
alert(textStatus);
}
});