Prev: DBTYP.NET Studio 2010 - Database Comparison Suite Released
Next: Multi-threading question
From: Curious on 10 Mar 2010 21:58
Given a generic list of items, when each item has some attributes such
as name, age, etc.

How to get a sublist of the items filtered by an attribute, (say age =
40)?

I can only think of looping through each item on the list, and check
to see if its age is 40. Is there more efficient way(s) to do this?
From: Mr. Arnold on 10 Mar 2010 23:08
Curious wrote:
> Given a generic list of items, when each item has some attributes such
> as name, age, etc.
>
> How to get a sublist of the items filtered by an attribute, (say age =
> 40)?
>
> I can only think of looping through each item on the list, and check
> to see if its age is 40. Is there more efficient way(s) to do this?

It's called LINQ.

var thelist = (from a in list.where(a => a.age == 40)select a).tolist();

http://en.wikipedia.org/wiki/Language_Integrated_Query
From: gerry on 11 Mar 2010 12:33
that's a pretty convoluted mixing of metaphors , to put it much simpler :

var thelist = list.Where(a => a.age == 40);

or

var = from a in list where a.age==40 select a;


"Mr. Arnold" <Arnold(a)Arnold.com> wrote in message
news:eVgx3BNwKHA.732(a)TK2MSFTNGP06.phx.gbl...
> Curious wrote:
>> Given a generic list of items, when each item has some attributes such
>> as name, age, etc.
>>
>> How to get a sublist of the items filtered by an attribute, (say age =
>> 40)?
>>
>> I can only think of looping through each item on the list, and check
>> to see if its age is 40. Is there more efficient way(s) to do this?
>
> It's called LINQ.
>
> var thelist = (from a in list.where(a => a.age == 40)select a).tolist();
>
> http://en.wikipedia.org/wiki/Language_Integrated_Query


From: Mr. Arnold on 11 Mar 2010 21:35
gerry wrote:
> that's a pretty convoluted mixing of metaphors , to put it much simpler :
>
> var thelist = list.Where(a => a.age == 40);
>
> or
>
> var = from a in list where a.age==40 select a;

I don't know what you're talking about. And I don't think you know what
you're talking about.

Do you know anything about this?

http://msdn.microsoft.com/en-us/library/bb397687.aspx

(var =) I don't think that's going to work anywhere but giving a compile
error.

var thelist = (from a in list.where(a => a.age == 40)select a)tolist();

var list = (from a in accounts1.OrderBy(b => b.Lastname).Where(c =>
c.Age == 40)).tolist();

Do you not see the power of the expression?

You should have been posting to the OP and not me.

The next time you get in someone's face with a bunch of nonsense you had
better be correct yourself.
From: gerry on 12 Mar 2010 17:38

"Mr. Arnold" <Arnold(a)Arnold.com> wrote in message
news:eI9XLzYwKHA.5940(a)TK2MSFTNGP02.phx.gbl...
> gerry wrote:
>> that's a pretty convoluted mixing of metaphors , to put it much simpler :
>>
>> var thelist = list.Where(a => a.age == 40);
>>
>> or
>>
>> var = from a in list where a.age==40 select a;
>
> I don't know what you're talking about. And I don't think you know what
> you're talking about.

huh - other than the 'var =' typo - what's the problem ?

>
> Do you know anything about this?
>
> http://msdn.microsoft.com/en-us/library/bb397687.aspx
>

sure I use it all the time

> (var =) I don't think that's going to work anywhere but giving a compile
> error.

if we are going to get typographically picky here - did you try to compile
the original example you gave ? Even the new one added below here won't
compile as is.

>
> var thelist = (from a in list.where(a => a.age == 40)select a)tolist();
>
> var list = (from a in accounts1.OrderBy(b => b.Lastname).Where(c => c.Age
> == 40)).tolist();
>
> Do you not see the power of the expression?

Sure I do - I also see the unnecessary complexity, jumble and
innefficiency - do you ?
Personally I try not to mix linq query syntax with & lambda expressions
whenever possible - KISS.

In your original example : ( note the corrections - the original code would
not compile ! )
var thelist = (from a in list.Where(a => a.age == 40)select a).ToList();
the segment
(from a in list.Where(a => a.age == 40)select a
is functionally equivalent to both
from a in list where a.age == 40 select a
and
list.Where(a => a.age == 40)
Depending on the usage .Tolist() could be unnecessary, if for some reason
you really need it then
list.Where(a => a.age == 40).ToList()
will do it, by responding that either
var thelist = list.Where(a => a.age == 40);
or
var thelist = from a list where age == 40 select a;
are both simpler ( less convoluted ) than
var thelist = (from a in list.Where(a => a.age == 40)select a)ToList();
is just stating the obvious

similarly with the 2nd newly added example , either
var list = from a in accounts1 where a.Age == 40 orderby a.Lastname
select a;
or
var list = accounts1.Where(a => a.Age == 40).OrderBy(a => a.Lastname);
are both perferable to
var list = (from a in accounts1.OrderBy(b => b.Lastname).Where(c =>
c.Age == 40)).tolist();
both in readablilty and efficiency.


>
> You should have been posting to the OP and not me.
>

I was replying to the thread, not to you.

> The next time you get in someone's face with a bunch of nonsense you had
> better be correct yourself.

in whose face how and with what nonsense ?
as noted above - your examples were/are incorrect as well.

just out of curiosity - why did you change your original link from
http://en.wikipedia.org/wiki/Language_Integrated_Query to
http://msdn.microsoft.com/en-us/library/bb397687.aspx
and add the second linq example as if it was part of your original response
?



 |  Next  |  Last
Pages: 1 2 3
Prev: DBTYP.NET Studio 2010 - Database Comparison Suite Released
Next: Multi-threading question