Why did they use this C# syntax to create a list of links in ASP.NET MVC 2?

Question

I'm having hard time understanding the following C# code. This code was taken from Pro ASP.NET MVC 2 Framework by Steven Sanderson. The code esentially creates URLs based on a list of categories.

Here's the code:

        Func<string, NavLink> makeLink = categoryName => new NavLink { 
            Text = categoryName ?? "Home", 
            RouteValues = new RouteValueDictionary(new { 
                controller = "Products", 
                action = "List", 
                category = categoryName, 
                page = 1 
            }),
            IsSelected = (categoryName == currentCategory)

A lot of stuff is going on here. I'm guessing it's defining a function that expects two parameters of type string, and NavLink. Then I see the Lambda categoryName => new NavLink etc.... I think all it's doing is creating an instance of NavLink.

The function is then called in the same Controller action:

        // Place home link on top
        List<NavLink> navLinks = new List<NavLink>();
        navLinks.Add(makeLink(null));

        // Add link for each distinct category
        var categories = productsRepository.Products.Select(x => x.Category.Name);
        foreach (string categoryName in categories.Distinct().OrderBy(x => x))
            navLinks.Add(makeLink(categoryName));

I can tell that it's making a list of NavLink. I don't understand why Steven Sanderson wrote it this way though. Couldn't he have written something like:

var categories = productsRepository.Products.Select(x => x.Category.Name);
foreach (string categoryName in categories.Distinct().OrderBy(x => x))
{
    var newlink = new Navlink{
        text = categoryName,
        RouteValues = new RouteValueDictionary(new {
           controller = "Products",
           action = "List",
           category = categoryName,
           page = 1
        }),
        IsSelected = (categoryName == currentCategory)
    }
    navLinks.Add(newlink);
}

Is there an advantage to doing it Steven's way versus my way?

Answer 1

It looks like that he wanted to use a local function that can be used for both adding the home link and as part of the categories loop. If he did it in-line like you did he would have to almost repeat the same code just for the single home link.

Answer 2

Overuse of any advanced and cool construct just because it's advanced and cool usually doesn't result in anything but poor readability. Unless the lambda is used in some special sophisticated tricky way elsewhere, I would use a plain old private method instead...

Edit: It's worth adding that “special sophisticated tricky ways” shall be at least commented appropriately…