c# - Mvc ActionResult redirect using Json on success

Question

I'm attempting to redirect users after successfully completing a form.

Controller:

public ActionResult Create(Acquisition acquisitions)
{
    return Json(new
    {
        redirectUrl = Url.Action("Index", "Acquisitions"),
        isRedirect = true
    });
}

After adding the return Json to my controller I'm getting this error message:

Error 6 The type 'System.Web.Routing.RouteValueDictionary' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Web, Version=4.0.0.0, Culture=neutral...

JavaScript:

$.ajax({
    type: "POST",
    url: "/Acquisitions/Create",
    data: $("form").serialize(),
    success: function (data) {
        if (data.isRedirect) {
            window.location.href = data.redirectUrl;
        }
    },
    error: function () {
        alert("error");
    }
});