jQuery Ajax calls and the Html.AntiForgeryToken()

Question

I have implemented in my app the mitigation to CSRF attacks following the informations that I have read on some blog post around the internet. In particular these post have been the driver of my implementation

• Best Practices for ASP.NET MVC from the ASP.NET and Web Tools Developer Content Team
• Anatomy of a Cross-site Request Forgery Attack from Phil Haack blog
• AntiForgeryToken in the ASP.NET MVC Framework - Html.AntiForgeryToken and ValidateAntiForgeryToken Attribute from David Hayden blog

Basically those articles and recommendations says that to prevent the CSRF attack anybody should implement the following code:

1) Add the [ValidateAntiForgeryToken] on every action that accept the POST Http verb

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult SomeAction( SomeModel model ) {
}

2) Add the <%= Html.AntiForgeryToken() %> helper inside forms that submits data to the server

<div style="text-align:right; padding: 8px;">
    <%= Html.AntiForgeryToken() %>
    <input type="submit" id="btnSave" value="Save" />
</div>

Anyway in some parts of my app I am doing Ajax POSTs with jQuery to the server without having any form at all. This happens for example where I am letting the user to click on an image to do a specific action.

Suppose I have a table with a list of activities. I have an image on a column of the table that says "Mark activity as completed" and when the user click on that activity I am doing the Ajax POST as in the following sample:

$("a.markAsDone").click(function (event) {
    event.preventDefault();
    $.ajax({
        type: "post",
        dataType: "html",
        url: $(this).attr("rel"),
        data: {},
        success: function (response) {
            // ....
        }
    });
});

How can I use the <%= Html.AntiForgeryToken() %> in these cases? Should I include the helper call inside the data parameter of the Ajax call?

Sorry for the long post and thanks very much for helping out

EDIT:

As per jayrdub answer I have used in the following way

$("a.markAsDone").click(function (event) {
    event.preventDefault();
    $.ajax({
        type: "post",
        dataType: "html",
        url: $(this).attr("rel"),
        data: {
            AddAntiForgeryToken({}),
            id: parseInt($(this).attr("title"))
        },
        success: function (response) {
            // ....
        }
    });
});

Answer 1

I use a simple js function like this

AddAntiForgeryToken = function(data) {
    data.__RequestVerificationToken = $('#__AjaxAntiForgeryForm input[name=__RequestVerificationToken]').val();
    return data;
};

Since every form on a page will have the same value for the token, just put something like this in your top-most master page

<%-- used for ajax in AddAntiForgeryToken() --%>
<form id="__AjaxAntiForgeryForm" action="#" method="post"><%= Html.AntiForgeryToken()%></form>  

Then in your ajax call do (edited to match your second example)

$.ajax({
    type: "post",
    dataType: "html",
    url: $(this).attr("rel"),
    data: AddAntiForgeryToken({ id: parseInt($(this).attr("title")) }),
    success: function (response) {
        // ....
    }
});