Comments on: Hacking LINQ Expressions: Select With Index

By: Chris Missal

Chris Missal — Tue, 15 Sep 2009 22:14:22 +0000

This made a lot more sense after I saw you code it. :)

By: Keith Dahlby

Keith Dahlby — Tue, 15 Sep 2009 13:26:26 +0000

You certainly could inline the Select call within a query, however you’re then stuck using an anonymous type and an “extra” variable. You either end up with variables like x with properties like y that mean nothing, or code that looks like this:

from ProductWithIndex in Products.Select((p,i) => new { Product = p, Index = i })
where ProductWithIndex.Product.IsSpecial()
select new { ProductWithIndex.Index, ProductWithIndex.Product.ID };

By leaning on the query expression, that intermediate identifier (x or ProductWithIndex) becomes transparent. So in the body of the Join we have access to x, y and i without having to mess with any secondary types and unintuitive x.y syntax.

At that point the query vs. method translation comes down to the same question as always: is the query inflexibility made up for by the value of clean expression of intent?

By: Stephen

Stephen — Tue, 15 Sep 2009 09:59:21 +0000

As you say, its a hack- ultimately I’m not sure the linq syntax is always that great, and I often just write the extension methods directly instead.. I would think you could just have done:

from x in seq.Select((y, i) => new { y, i })

or write an extension method:

from x in seq.WithIndexes()