How to refactor these 2 similar methods into one?

Question

I\'ve seen some samples of using \'T\' to make a method reuseable for generic collections of different classes, but I\'ve never really gotten into it or understood the samples.

Answer 1

Without implementiong a common interface like @Grzenio suggested, you could use a generic method like this:

    public List ToSelectList(IEnumerable enumerable, Func text, Func value, string defaultOption)
    {
        var items = enumerable.Select(f => new SelectListItem() { Text = text(f), Value = value(f) }).ToList();
        items.Insert(0, new SelectListItem() { Text = defaultOption, Value = "-1" });
        return items;
    }

    // use like

    t.ToSelectList(departments, d => d.Code + " - " + d.Description, d => d.Id.ToString(), "default");
    t.ToSelectList(functions, f => f.Description, f => f.Id.ToString(), "default");