- Getting to Know the BirdWatcher Data 2:17
- How Much Data Do We Have? 6:25
- Operators Review 3 questions
- Sightings of Endangered Birds 7:11
- Bird Importing 8:40
- Bird Search Extension 11:44
- Bird Search In Action 7:45
- Extension Method 2 objectives
- Which is Faster? Union versus Concat 6:57
- Some Final Advice 3:15
- Final Advice 3 questions
Preview
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How Much Data Do We Have?
6:25Let's build some LINQ queries to get familiar with our new data set.
Our workspaces has all the new and
improved classes for us.
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You can follow along in the example,
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just like we did before,
with the same steps,
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csharp, LoadAssembly("BirdWatcher.dll"),
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and using BirdWatcher,
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then we'll load up our birds,
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var birds = BirdRepository.LoadBirds.
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Okay, let's explore our data a little
by getting some record counts.
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Let's see how many birds we're
dealing with here, birds.Count.
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That's a decent number.
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Now, how many sightings do we have?
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Each bird has a list of sightings, so
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we can perform a select on all
the birds to get all the sightings and
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then call the count method, birds.Select,
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b goes to b.Sightings, and Count.
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Wait, that can't be right.
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There's no way that each
bird only has one sighting.
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I forgot to use select many,
the select method returned to us
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an innumerable of sighting sequences for
each bird.
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So we just counted how many collections
of sightings there are total, and
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not the sightings themselves.
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Let's try that again,
this time using select many to
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flatten out the sightings
into one collection,
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birds.SelectMany, where
b goes to b.Sightings,
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and then we'll call count.
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Now that's better.
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A decent number for us to work with.
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Let's see, what's the average
sighting count per bird in our data?
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Well, we can use the total
number of sightings and
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then put it over the total
number of birds, right?
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Nine, well, you know there's
a better way we can do that,
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we can use the average method instead.
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So, since we want the average
of the total count per bird,
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we should use select to get a sequence
of the total counts, you follow?
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Select b goes to b.Sightings.Count,
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and then we'll call Average.
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That worked, and it looks like it
was a little more accurate too.
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Well, now I'm wondering how many different
countries we have bird sighting data in.
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Let's see, so
to get to the country of each sighting,
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we'll need to access the place
property of sighting.
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Well, you select many first to
get a flat list of sightings,
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birds.SelectMany, b goes to b.Sightings.
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So, that'll give us a big
collection of all the sightings.
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Then, we need to get each habitat on each
sighting, not habitat, I think it's place.
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Let's check just to make sure.
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So on the sighting, class,
yep, it's called place.
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So, we'll need to call a select, where s,
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I'll use s,
since we're dealing with sightings now,
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goes to s.Place, and then .Country, so
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that should return all of our countries.
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Well, I got an extra space here.
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All right, now that we've got
a giant list of country strings,
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we can use distinct to get a list
of the distinct countries.
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So I'll press up to get my last command,
and I'll call Distinct.
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All right, that's a little better.
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Now, let's see how many
sightings are in each country.
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Usually when I hear the phrase,
in each, or the word, by,
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as in count of sightings by country,
I know that I'll need to use a grouping.
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Let's start out with all our sightings,
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birds.SelectMany, b goes to b.Sightings,
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then we'll need a GroupBy, so .GroupBy,
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and then we'll group by the country, so
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that's GroupBy, s goes to s.Place.Country.
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All right, let's see what that gives us.
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Wow [LAUGH], so we've got a bunch
of groups of sighting objects,
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and the key should be countries, so
now to get the final count by country,
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we'd need to perform a select, and
then create an anonymously typed object.
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So, I'll tack on a Select method,
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Select, and
I'll say group instead of a letter.
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We're gonna do an anonymous type here,
so new,
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curly brace, and the country,
should be the grp.Key,
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and then the Sightings is what we'll
call the account, and grp.Count.
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Okay, let's see what I did there.
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Got an extra space again.
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Let's try that.
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Okay, so it looks like we've got,
Canada's got 200,
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the US has 233,
200 in pretty much each country.
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Feel free to play around a little more and
write some link queries for
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our bird data before we
get to the next video.
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