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From: "Steve D" <nospam_steved94@comcast.net>
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Subject: Re: Lambda expressions? LINQ?
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Date: Fri, 18 Sep 2009 19:33:51 -0700
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Date: 2009-09-18T19:33:51-07:00
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>"sjw" <simon.j.wright@mac.com> wrote in message 
>news:9b330aae-2c83-4d1c-995b-192425cd1c52@m11g2000vbl.googlegroups.com...
>On Sep 18, 2:59 am, "Steve D" <nospam_steve...@comcast.net> wrote:
>> "Jeffrey R. Carter" <spam.jrcarter....@spam.acm.org> wrote in 
>> messagenews:h8qf72$jv2$2@news.tornevall.net...
>>
>> > Steve D wrote:
>>
>> >> Using LINQ and the .NET framework I was able to query an XML document 
>> >> for
>> >> all elements with a given element name, select an attribute with a
>>> >> specific name, split the content of the attribute (a comma separated 
>>> >> list
>> >> of strings) into it's individual strings and return an array of unique
>> >> elements... in one line of source code. ... Wow!
>>
>> > Sounds like a write-only language to me.
>>
>> Oh, so you are familiar with LINQ and find that you cannot make queries 
>> that
>> are readable?
>> My experience is not the same.
>
>It would certainly be interesting to see this one-liner (or even an
>approximation to it!).

As Martin guessed it is one statement spread over a few lines.

            string[] names = xDoc.Descendants("Layer0Message")
                              .SelectMany(node => 
node.Attribute("To").Value.Split(' ',',').Where( st => st.Length > 0 ))
                                  .Distinct().OrderBy(n=>n).ToArray();

There is an alternate way of formatting the query... more like SQL, but I 
prefer the version that uses the dot notation.

Here's a small chunk of the XML data it is reading:

<File>
  <!-- Message #1 -->
  <NewMessage>
    <Time>10:08:19.812</Time>
    <Layer0Message Type="2000" Name="MAL_RAW_ENCODER" From="encoder" To=" 
sequencer, turnset" OriginalBytes="12" SavedBytes="12" DataFormat="INT8 HEX" 
/>
    <Data>63 BF F4 C0 C7 3C 02 00 C3 4F 4F 14 </Data>
  </NewMessage>
  <!-- Message #2 -->
  <NewMessage>
    <Time>10:08:19.812</Time>
    <Layer0Message Type="2210" Name="ROTATION_MEASUREMENT" From="rda" To=" 
turnset" OriginalBytes="6" SavedBytes="6" DataFormat="INT8 HEX" />
    <Data>88 3D 5A C2 32 BD </Data>
  </NewMessage>


Oh, and by the way.  LINQ isn't just for XML.  You can do queries on arrays, 
lists, etc.  For example if you have an array of records you can do a query 
to select all of the records with a field that has a particular value.  It's 
cool.

I just wish my favoriate language had this feature.

Regards,
Steve