/// <summary>
/// Creates a column header cell (<c>td</c>) that is sortable (the user can click on it to sort
/// ascending/descending)
/// </summary>
/// <typeparam name="T">The type being displayed in the view</typeparam>
/// <typeparam name="TProp">The type of the property whose column header is being created</typeparam>
/// <param name="html">The <see cref="HtmlHelper{T}"/></param>
/// <param name="viewData">
/// The <see cref="PagedSortedViewModel{T}"/> view data from the <see cref="HtmlHelper{T}"/>
/// </param>
/// <param name="propertySelector">
/// A lambda expression that returns one of the properties on the object
/// </param>
/// <param name="text">The text to display in the column header cell</param>
/// <param name="routeValues">
/// The route values to include in the link that allows sorting. This can be null, which will cause the
/// current page's route and URL parameters to be used
/// </param>
/// <param name="sortRouteValueName">
/// The route value name used to store the sorting settings string in. This can be null which will
/// cause the value <c>sort</c> to be used
/// </param>
/// <param name="htmlAttributes">Html attributes to apply to the <c>th</c> tag</param>
/// <returns>The HTML</returns>
private static MvcHtmlString SortableColumnHeader <T, TProp>(this HtmlHelper html, PagedSortedViewModel <T> viewData, Expression <Func <T, TProp> > propertySelector, string text, RouteValueDictionary routeValues, string sortRouteValueName, IDictionary <string, object> htmlAttributes)
{
UrlHelper url = new UrlHelper(html.ViewContext.RequestContext);
sortRouteValueName = sortRouteValueName ?? "sort";
routeValues = routeValues ?? url.RouteToCurrentPage();
htmlAttributes = htmlAttributes ?? new Dictionary <string, object>();
Sorter <T> sorter = viewData.Sorter;
bool sortDirection;
KeyValuePair <LambdaExpression, bool> selectorPair = sorter.OrderedPropertySelectors[0];
bool isFirstSort = sorter.PropertySelectorsEqual(propertySelector, selectorPair.Key);
if (isFirstSort)
{
sortDirection = !selectorPair.Value;
}
else
{
sortDirection = true;
}
bool currentSortDirection = sorter.GetSortDirectionForProperty(propertySelector);
RouteValueDictionary routeDictionary = new RouteValueDictionary(routeValues);
routeDictionary[sortRouteValueName] = sorter.Clone().SortBy(propertySelector, sortDirection).Encode();
TagBuilder th = new TagBuilder("th");
TagBuilder a = new TagBuilder("a");
string linkTitle = String.Format("{0} (Sorted {1})", text, (currentSortDirection ? "Ascending" : "Descending"));
a.MergeAttribute("title", linkTitle);
a.MergeAttribute("href", url.RouteUrl(routeDictionary));
th.AddCssClass("Sortable");
if (isFirstSort)
{
th.AddCssClass("PrimarySortColumn");
}
else
{
th.AddCssClass("NonPrimarySortColumn");
}
if (currentSortDirection)
{
th.AddCssClass("SortedAscending");
}
else
{
th.AddCssClass("SortedDescending");
}
a.InnerHtml = text;
th.InnerHtml = a.ToString();
th.MergeAttributes(htmlAttributes);
return(MvcHtmlString.Create(th.ToString()));
}