Question

I have a number of class objects, each of which needs a URL field which is always formatted in the same way via parameter TypeId, another property of the class.

What is the best way to abstract this as a dynamic property so the URL field is generated based on the TypeId and ItemId properties from the class.

I can think of many ways to do this but wondered what the recommended practice was.

Example below:

public class MyObject
{
    public int Id { get; set; }
    public string URL
    {
        get
        {
            if (TypeId == 3)
            {
                return "/do/this/" + ItemId;
            }
            if (TypeId == 5)
            {
                return "/do/that/" + ItemId;
            }
            return "#";
        }
    }
    public int ItemId { get; set; }
    public int TypeId { get; set; }
}

Answer 1

You could set up a dictionary with all of the known TypeIds and a Func<int, string> to return the URL. You could even make it so new TypeIds and URL-formatting functions could be added at runtime:

private Dictionary<int, Func<int, string>> _urlFormatters;

public string URL
{
    get { return _urlFormatters[TypeId](ItemId); }
}

// In the constructor or some other init area:
{
    _urlFormatters = new Dictionary<int, Func<int, string>>
        {
            { 3, itemId => "/do/this/" + itemId },
            { 5, itemId => "/do/that/" + itemId }
        };
}