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A DD4T.net Implementation - Navigtion Utils

In the previous posts Navigation and Navigation (part 2), I presented the NavigationFactory class and the object model obtained by deserializing the navigation XML.

In this post, I will present simple examples of creating breadcrumb and navigation structures.

Breadcrumb

When rendering a breadcrumb trail, we start by locating the NavigationItem in the navigation object model corresponding to the current page, and then we follow the "ParentItem" relation to go up until the navigation root. We retain each NavigationItem that we encounter in this traversal. Finally, the breadcrumb trail is the reversed list of these NavigationItems.

The following code is part of the NavigationFactory and returns an array of NavigationItem objects corresponding to the breadcrumb trail.

public NavigationItem[] GetBreadcrumb(NavigationItem page)
{
    IList<NavigationItem> result = new List<NavigationItem>();
    if (page != null)
    {
        do
        {
            result.Add(page);
            page = page.ParentItem;
        }
        while (page != null);
    }

    return result.Reverse().ToArray();
}

The method GetBreadcrumb expects a NavigationItem object as parameter, which means we first need to get the NavigationItem for the current IPage. The method below builds such a NavigationItem array for the given IPage. The code checks whether the current page is in the Navigation, or otherwise whether its Structure Group is in the navigation object model.

private List<NavigationItem> GetBreadcrumbForPage(IPage page)
{
    NavigationItem item = NavigationFactory.GetItemById(Navigation, page.Id) ??
        NavigationFactory.GetItemById(Navigation, page.StructureGroup.Id);

    return GetBreadcrumbForNavigationItem(item);
}

Once the NavigationItem corresponding to the current IPage has been identified, we call method GetBreadcrumbForNavigationItem which builds the actual breadcrumb. Notice that we discard the first element in the returned array, because this corresponds to the Root Structure Group.

Additionally, the code checks whether the last element in the breadcrumb is a default page (e.g. default.aspx), and if so, it removes it.

private List<NavigationItem> GetBreadcrumbForNavigationItem(NavigationItem item)
{
    List<NavigationItem> result = new List<NavigationItem>(NavigationFactory.GetBreadcrumb(item));
    if (result.Count > 0)
    {
        result.RemoveAt(0);

        NavigationItem lastItem = result.LastOrDefault();
        if (lastItem != null && UriHelper.IsDefaultPage(lastItem.ActualUrl))
        {
            result.Remove(lastItem);
        }
    }

    return result;
}

Navigation

Rendering navigation implies getting the Navigation object model and traversing it top-bottom in order to generate the HTML structures for each level.

The following code exists in a Razor template and calls a partial view passing to it the NavigationItem array of the first level items in the navigation:

    @Html.Partial("_PartialNavigation", Html.GetNavigations((IPage)Model))

The method GetNavigations is defined as extension method for HtmlHelper and it is in charge with reading the navigation items directly under the root Structure Group:

public static IList<NavigationItem> GetNavigations(this HtmlHelper htmlHelper, IPage page)
{
    if (page == null)
    {
        return new NavigationItem[0];
    }
    INavigationFactory navigationFactory = DependencyResolver.Current.GetService<INavigationFactory>();
    Navigation navigation = navigationFactory.GetNavigation();
    return new List<NavigationItem>(navigationFactory.GetNavigation(navigation));
}

The Razor view presented below belongs to file _PartialNavigation.cshtml and it shows some sample code that generates a two-level deep HTML navigation:

@model IList<NavigationItem>

<ul>
    @foreach (NavigationItem levelOne in Model)
    {
        <li>
            <a href="@levelOne.Url">@levelOne.Title</a>
            <ul>
                @foreach (NavigationItem levelTwo in levelOne.ChildItems)
                {
                    <li>
                        <a href="@levelTwo.Url">@levelTwo.Title</a>
                    </li>
                }
            </ul>
        </li>
    }
</ul>


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