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In this video, we'll review the solution to the second and final challenge.
Finding an Element in an Array
As mentioned in the video, finding an element in an array is such a common thing to do, the .NET Framework Array type provides a static method for doing exactly that—the Find() method. Here's the documentation for the Find() method:
How did you do?
0:00
Let's take a look at my solution.
0:01
In the MediaLibrary class, I stubbed
out a method an item named find Item.
0:03
I did that right above
the DisplayItems method.
0:16
Public for the access modifier and
MediaType for the return type.
0:21
Then the name of the method FindItem
followed by a set of parentheses,
0:26
And I defined a parameter of
type string named criteria.
0:31
Then, within the method body,
I start it with defining the variable for
0:39
the MediaType item that will
return from the method.
0:43
MediaType, itemToReturn,
0:48
And we'll set it to null.
0:54
And as a habit, I try to remember to add
the code right now to return the variable.
0:57
That way, I won't forget to do it later.
1:03
Then in between declaring the itemToReturn
variable and returning it,
1:07
I added my for each loop.
1:12
For each, then a set of parentheses and
a set of curly braces.
1:15
Then within the set of
parentheses after the foreach
1:22
keyword, I added (var item in _items).
1:27
Remember that the foreach loop
will loop each item in the array.
1:32
We just need to declare a variable
to use for the item references here,
1:36
and provide the collection that
we want to loop over here.
1:42
Within the loop I added an if statement.
1:47
And for the condition I
called the contains method on
1:55
the item's title property,
passing in the criteria
2:00
parameter, item.Title.Contains criteria.
2:05
The string contains method will
return true if the provided string
2:12
is contained within the string
that you’ve called the method on.
2:17
One downside of this approach is that
the contains method is case sensitive.
2:21
This means that a string that starts with
a capital letter won’t match a string that
2:26
starts with a lower case letter.
2:30
This behavior might not be what
consumers of our class would expect.
2:32
To work around this issue, we can force
both of the strings in our condition to
2:36
lower case letters by
calling the ToLower method.
2:41
So item.ToLower, And
2:46
then on criteria.ToLower.
2:52
Now it doesn't matter that the contains
method is case sensitive because both
2:57
strings will be converted to lower case
letters before the comparison is done.
3:02
Then within the if statement I assigned
the itemToReturn variable to the item loop
3:09
variable And
3:14
I added a break statement to exit the loop
as soon as we found a matching item.
3:21
And that completed my find
item method implementation.
3:32
Then in the program.cs file,
3:37
I started by commenting out all of
the code below the instantiation of
3:43
the MediaLibrary object.
3:48
And then I added a call
to the find item method.
3:57
Var item = mediaLibrary.FindItem and
4:00
for the criteria,
4:06
I passed in arabia with a lowercase a.
4:09
From there, I needed to check to
see if an item was found or not, so
4:17
I stubbed out an if else statement.
4:22
For the condition I checked
if the item wasn't null.
4:32
So, (item != null).
4:35
Checking if the item is null or
not works because I'm returning null
4:40
from the find item method if
a matching item isn't found.
4:45
Within the if statement,
4:49
I added a call to the
mediaLibrary.DisplayItems static method.
4:51
So that's MediaLibrary with a capital M
because we're calling is static method.
4:57
Then .DdisplayItem, and
I'll pass in the item to display.
5:02
And within the else statement I added
a call to the Console.writeLine method,
5:13
passing in the string, item not found
5:18
And lastly, I saved my file,
I compiled and
5:30
I ran my program in order
to test my changes.
5:33
And I've received a compilation error Type
'Treehouse.MediaLibrary.MediaType' does
5:55
not contain a definition for 'Tolower' and
no extension method 'Tolower' of
6:00
type 'Treehouse.MediaLibrary.MediaType'
could be found.
6:05
Let's take a look at that code and
see what I did.
6:09
Here it is.
6:16
I'm trying to call ToLower on item instead
of calling ToLower on the title property.
6:17
That's an easy mistake to make.
6:23
So now it's item.Title property.
6:30
Which is a string,
which we then can call ToLower on.
6:35
I'll save, and
try to compile my program again.
6:40
And now we can see that an item was found
whose title contains the string, Arabia.
6:48
Now let's try changing our search criteria
to something that won't be found in our
6:58
media library.
7:03
How about the word, toy?
7:07
Then let's compile and
run our program again.
7:17
And now we can see that
an item wasn't found.
7:22
Great job.
7:27
Finding an element in an array
is such a common thing to do.
7:29
The .NET framework array type
actually provides a static method for
7:32
doing exactly that, the find method.
7:37
See the teachers notes for
more information.
7:40
When learning the language,
library or framework,
7:42
it's not unusual to overlook
a built-in feature.
7:45
This is a good remainder to
always consult the documentation.
7:48
Getting into the habit of doing that
will save you time by not building or
7:52
implementing features that you don´t need.
7:56
Nice job completing this practice session.
7:59
Thanks for practicing with me and
we´ll see you next time.
8:02
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