ActionLink with multiple parameters

The overload you are using makes the year value end up in the html attributes of the link (check your rendered source).

The overload signature looks like this:

MvcHtmlString HtmlHelper.ActionLink(
    string linkText, 
    string actionName, 
    string controllerName, 
    object routeValues, 
    object htmlAttributes
)

You need to put both your route values in to the RouteValues dictionary like this:

Html.ActionLink(
    "View Details", 
    "Details", 
    "Performances", 
    new { name = item.show, year = item.year }, 
    null
)

In addition to Mikael Östberg answer add something like this in your global.asax

routes.MapRoute(
    "View Details",
    "Performances/Details/{name}/{year}",
    new {
        controller ="Performances",
        action="Details", 
        name=UrlParameter.Optional,
        year=UrlParameter.Optional
    });

then in your controller

// the name of the parameter must match the global.asax route    
public action result Details(string name, int year)
{
    return View(); 
}

Based on Mikael Östberg answer and just in case people need to know how it does with html attr. Here is another example, reference from ActionLink

@Html.ActionLink("View Details", 
"Details", 
"Performances", 
  new { name = item.show, year = item.year }, 
  new {@class="ui-btn-right", data_icon="gear"})


@Html.ActionLink("View Details", 
"Details", 
"Performances", new RouteValueDictionary(new {id = 1}),new Dictionary<string, object> { { "class", "ui-btn-test" }, { "data-icon", "gear" } })