Linq "into" and "let" equally???

[Alexander Vasilevsky]

Linq "into" and "let" equally???

http://www.alvas.net - Audio tools for C# and VB.Net developers

[Jon Skeet [C# MVP]]

Frans Bouma [C# MVP] <pe************ ******@xs4all.n lwrote:

LINQ isn't actually set-oriented - it's sequence-oriented, a
pipeline. It may be convenient to think in terms of sets when
writing LINQ to SQL, but LINQ to Objects should definitely be
considered in terms of sequences.

A query which is executed on a db, will end up as a set-oriented
statement.

Yes. And a query which is executed in-process will end up as a
sequence-oriented statement.

If you write your query as imperative as possible, you WILL
probably have a slow query. A query written to be executed on a DB
should be written with set operations in mind, otherwise you will end
up sooner or later at the wrong end of the DBA-developer conversation
where you need to optimize the query to make it performing properly but
you don't know how.

It depends on what you mean by "as imperative as possible". I don't see
"let" as being particularly imperative - you could regard it as
assigning an alias. The test queries I've done against LINQ to SQL
(which aren't many, admittedly) look fine to me.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
World class .NET training in the UK: http://iterativetraining.co.uk

[Jon Skeet [C# MVP]]

On Nov 26, 8:33 am, "Frans Bouma [C# MVP]"
<perseus.usenet NOS...@xs4all.n lwrote:

It depends on what you mean by "as imperative as possible". I don't
see "let" as being particularly imperative - you could regard it as
assigning an alias. The test queries I've done against LINQ to SQL
(which aren't many, admittedly) look fine to me.

Example: (I used 'from' here to make it more clear, I also could have
used let, it would result in a SelectMany as well)

No, "let" doesn't result in SelectMany - it results in another Select.

From the spec:

"A query expression with a let clause
from x in e
let y = f
....
is translated into
from * in ( e ) . Select ( x =new { x , y = f } )"

Does that change your opinion of it?

Jon