I guess that simpler approach might be for eample following:

builder usage:
var product = ProductBuilder
.CreateProduct()
.Customized( product =>
{
product.Name = “…”;
product.Priced = 273;
});

Builder code:
public ProductBuilder Customized(Action action)
{
_actions.Add(action);
return this;
}

the old builder method would be:
public ProductBuilder Named (string name)
{
_actions.Add(product => product.Name = name);
return this;
}

private Product Build()
{
var product = new Product();
// apply modifications
_actions.ForEach(action => action(product));
return product;
}

Couple of things:

This looks like a lot of work. I’m not saying it isn’t worth it, particularly for a public facing API. It just looks like something that can get out of hand with a larger and more substantial problem space.

What would be interesting here is to provide the progressions in order, so that a logical chain of calls could be enforced. Methods could then be chained in a stateful way. Don’t know that this is a good idea, but interesting, eh?

Of course, this could be done with a ridiculous chain of tiny interfaces using the method you prescribe here. Perhaps contracts in C#4 will offer something here. I haven’t looked yet.

http://www.clariusconsulting.net/blogs/kzu/archive/2008/03/10/58301.aspx