MVC 3 Layout Page, Razor Template, and DropdownList

As usual you could start by defining a view model:

public class YearsViewModel
{
    public string Year { get; set; }
    public IEnumerable<SelectListItem> Years
    {
        get
        {
            return new SelectList(
                Enumerable.Range(1900, 112)
                .OrderByDescending(year => year)
                .Select(year => new SelectListItem
                {
                    Value = year.ToString(),
                    Text = year.ToString()
                }
            ), "Value", "Text");
        }
    }
}

Then a controller:

public class YearsController : Controller
{
    public ActionResult Index()
    {
        return View(new YearsViewModel());
    }

    [HttpPost]
    public ActionResult Index(int year)
    {
        // TODO: do something with the selected year
        return new EmptyResult();
    }
}

and a corresponding view for the index action:

@model SomeAppName.Models.YearsViewModel
@{
    Layout = null;
}
@Html.DropDownListFor(x => x.Year, Model.Years)

And finally inside your _Layout.cshtml you could use this controller:

<div id="selectyear">@Html.Action("index", "years")</div>

and attach a corresponding script which would send an AJAX request when the value changes:

$(function () {
    $('#selectyear select').change(function () {
        $.post('@Url.Action("index", "years")', { year: $(this).val() }, function (result) {

        });
    });
});