How to add “active” class to Html.ActionLink in ASP.NET MVC

In Bootstrap the active class needs to be applied to the <li> element and not the <a>. See the first example here: http://getbootstrap.com/components/#navbar

The way you handle your UI style based on what is active or not has nothing to do with ASP.NET MVC's ActionLink helper. This is the proper solution to follow how the Bootstrap framework was built.

<ul class="nav navbar-nav">
    <li class="active">@Html.ActionLink("Home", "Index", "Home")</li>
    <li>@Html.ActionLink("About", "About", "Home")</li>
    <li>@Html.ActionLink("Contact", "Contact", "Home")</li>
</ul>

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Edit:

Since you will most likely be reusing your menu on multiple pages, it would be smart to have a way to apply that selected class automatically based on the current page rather than copy the menu multiple times and do it manually.

The easiest way is to simply use the values contained in ViewContext.RouteData, namely the Action and Controller values. We could build on what you currently have with something like this:

<ul class="nav navbar-nav">
    <li class="@(ViewContext.RouteData.Values["Action"].ToString() == "Index" ? "active" : "")">@Html.ActionLink("Home", "Index", "Home")</li>
    <li class="@(ViewContext.RouteData.Values["Action"].ToString() == "About" ? "active" : "")">@Html.ActionLink("About", "About", "Home")</li>
    <li class="@(ViewContext.RouteData.Values["Action"].ToString() == "Contact" ? "active" : "")">@Html.ActionLink("Contact", "Contact", "Home")</li>
</ul>

It's not pretty in code, but it'll get the job done and allow you to extract your menu into a partial view if you like. There are ways to do this in a much cleaner way, but since you're just getting started I'll leave it at that. Best of luck learning ASP.NET MVC!

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Late edit:

This question seems to be getting a bit of traffic so I figured I'd throw in a more elegant solution using an HtmlHelper extension.

Edit 03-24-2015: Had to rewrite this method to allow for multiple actions and controllers triggering the selected behavior, as well as handling for when the method is called from a child action partial view, thought I'd share the update!

public static string IsSelected(this HtmlHelper html, string controllers = "", string actions = "", string cssClass = "selected")
{
    ViewContext viewContext = html.ViewContext;
    bool isChildAction = viewContext.Controller.ControllerContext.IsChildAction;

    if (isChildAction)
        viewContext = html.ViewContext.ParentActionViewContext;

    RouteValueDictionary routeValues = viewContext.RouteData.Values;
    string currentAction = routeValues["action"].ToString();
    string currentController = routeValues["controller"].ToString();

    if (String.IsNullOrEmpty(actions))
        actions = currentAction;

    if (String.IsNullOrEmpty(controllers))
        controllers = currentController;

    string[] acceptedActions = actions.Trim().Split(',').Distinct().ToArray();
    string[] acceptedControllers = controllers.Trim().Split(',').Distinct().ToArray();

    return acceptedActions.Contains(currentAction) && acceptedControllers.Contains(currentController) ?
        cssClass : String.Empty;
}

Works with .NET Core:

public static string IsSelected(this IHtmlHelper htmlHelper, string controllers, string actions, string cssClass = "selected")
{
    string currentAction = htmlHelper.ViewContext.RouteData.Values["action"] as string;
    string currentController = htmlHelper.ViewContext.RouteData.Values["controller"] as string;

    IEnumerable<string> acceptedActions = (actions ?? currentAction).Split(',');
    IEnumerable<string> acceptedControllers = (controllers ?? currentController).Split(',');

    return acceptedActions.Contains(currentAction) && acceptedControllers.Contains(currentController) ?
        cssClass : String.Empty;
}

Sample usage:

<ul>
    <li class="@Html.IsSelected(actions: "Home", controllers: "Default")">
        <a href="@Url.Action("Home", "Default")">Home</a>
    </li>
    <li class="@Html.IsSelected(actions: "List,Detail", controllers: "Default")">
        <a href="@Url.Action("List", "Default")">List</a>
    </li>
</ul>

source https://stackoverflow.com/questions/7709001/html-actionlink-vs-url-action-in-asp-net-razor