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

In fact you can do it with a combination of generics and functions, something along the lines of this (untested may not even compile).

[NonAction]
public List ToSelectList(IEnumerable en, 
                                            Function text, 
                                            Function value, 
                                            string defaultOption)
{
    var items = en.Select(x => new SelectListItem() { Text = text(x) , Value = value(x) }).ToList();
    items.Insert(0, new SelectListItem() { Text = defaultOption, Value = "-1" });
    return items;
}

Then you can dispatch to it with the appropriate lambda functions (or call directly).

[NonAction]
public List ToSelectList(IEnumerable departments, 
                                         string defaultOption)
{
    return ToSelectList(departments, d =>  d.Code + '-' + d.Description, d => d.Id.ToString(), defaultOption);

}