Delegate Usage : Business Applications

Question

Background

Given that \'most\' developers are Business application developers, the features of our favorite programming languages are used in the context of what we

Answer 1

I think this question reflects the many ways to skin a cat. I find delegates (and lambdas) nearly as fundamental as a "for" loop.

Here's one context in which I used delegates recently (formatting and names changed for presentation purposes:)

protected T[] SortLines(Func createLine, IEnumerable unsorted)
where T : LineType
{
    Func, IEnumerable> sorter = (lines => lines);

    switch (settings.OrderSort)
    {
        case OrderSort.ByA: 
            sorter = (lines => lines.OrderBy(x => x.A)); break;
        case OrderSort.ByB:
            sorter = (lines => lines.OrderBy(x => x.B)); break;

        // and so on... a couple cases have several levels of ordering
    }

    bool requiresSplit = // a complicated condition
    if (requiresSplit)
    {
        var positives = unsorted.Where(x => x.Qty >= 0);
        var negatives = unsorted.Where(x => x.Qty <  0);

        return sorter(negatives).Concat(
               new T[] { createLine.Invoke() }).Concat(
               sorter(positives)).ToArray();
    }
    else
        return sorter(unsorted).ToArray();
}

So this sorts a group of items based on some criteria, and then it either returns the whole list sorted, or it breaks it in two, sorts both halves separately, and puts a separator in between them. Good luck doing this elegantly if you can't express the concept of "a way to sort something", which is what the delegate is for.

EDIT: I guess Concat and OrderBy are 3.0-specific, but this is still the basic idea.