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Using a `foreach` Loop

7:28 with James Churchill

In this video, we'll review the solution to the first challenge and introduce our second challenge—using a `foreach` loop to implement a method that'll give us a way to find a single item in our Media Library.

Teacher's Notes
Video Transcript
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Instructions

2nd Challenge

Add a method named FindItem() to the MediaLibrary class.
- The method should return a MediaType item and define a parameter of type string named criteria.
- Use a foreach loop to loop through the items array contained within the MediaLibrary class.
- Return the item whose Title property contains the provided criteria string parameter value.
In the Program.cs file, search the media library for an item by calling the FindItem() method.
- If an item is found, pass it into a call to the static MediaLibrary DisplayItem() method.
- If an item isn't found, write the message "Item not found!" to the console.

Finding a String Within Another String

There are many ways in C# to test if a string is contained within another string. Here's one approach that makes use of the String.Contains() method.

var songTitle = "Row Row Row Your Boat";
Console.WriteLine(songTitle.Contains("Your")); // Outputs "true" to the console
Console.WriteLine(songTitle.Contains("your")); // Outputs "false" to the console

This examples demonstrates one potential issue with this approach: the Contains() method is case-sensitive. As a workaround, we can call ToLower() on both the search criteria and item title.

var songTitle = "Row Row Row Your Boat";
Console.WriteLine(songTitle.ToLower().Contains("Your".ToLower())); // Outputs "true" to the console
Console.WriteLine(songTitle.ToLower().Contains("your")); // Outputs "true" to the console

By forcing all of the characters to lowercase, we're eliminating any case-sensitivity issues.

Here's the documentation on both the Contains() and ToLower() methods:

Help

If you get stuck on any of the following topics or simply need a refresher, click on a topic in list below to view the associated video in the C# Objects course.

Use a foreach loop to iterate through an array's items

Welcome back! 0:00

How did you do? 0:00

Let's walk through my solution. 0:01

In the MediaLibrary class, 0:03

I stubbed out a method named, 0:08

DisplayItems. 0:14

Within the method body, I added a for loop. 0:24

Remember that a for loop has three sections, 0:33

the initializer, the condition and the iterator sections. 0:36

The initilizer section is used to declare and initialize a local loop varible. 0:41

I declared the variable of type int named, index, And initialized it to 0. 0:47

This variable will be used to keep track of which array index we're 0:56

currently accessing within the loop. 1:01

The conditions section is used to determine when it's time to exit the loop. 1:03

I use the expression index 1:08

< _items.Length. 1:13

This expression will be evaluated right before each loop iteration. 1:22

The question, is the index variable less than the length of the _items array, 1:26

will be asked. 1:32

If yes, then the loop iteration is executed, 1:33

otherwise the loop will be exited. 1:37

And lastly, the iterator's section, which is used to define what 1:40

happens after each loop iteration, I used the expression index++. 1:44

The ++ operator, or the increment operator, 1:50

increments or increases the operand or variable by one. 1:55

After defining the initializer, condition, and iterator sections for 2:01

the for loop, I turned my attention to the implementation of the loop body. 2:06

To write each item's information to the console, 2:11

using the console writeline method, we can use its display text property. 2:14

But to get access to the display text property, 2:19

we first need to cast the item to its subtype. 2:22

You might remember though that we've already implemented a method that 2:25

already does all of this. 2:29

In the Progam.cs file, the Display method 2:33

provides the behavior that we're looking for. 2:37

Given that, I decided to move the Display method 2:43

from the Program.cs file to the MediaLibray class. 2:48

I selected the method and cut it to the clipboard. 2:54

Then I switched back to the MediaLibrary class file, 3:00

And pasted it from the clipboard, right below our DisplayItems method. 3:06

I left the method as a static method but added the public access modifier. 3:18

Making the method public will allow us to still call it from 3:23

the Program.cs file Main method. 3:27

But I decided to make the name of the method a little bit more descriptive. 3:29

So instead of just Display, I changed it to DisplayItem. 3:36

And I added a using directive for the system namespace. 3:44

So I didn't have to change these calls to the console WriteLine method. 3:47

Actually, after adding this using directive, 4:00

we can also update our GetItemAt method. 4:02

We no longer need System.here before the Console.WriteLine method call 4:10

With the DisplayItem method added, I added a call within the for loop body. 4:22

To get the reference to the item to display, I used the index local loop 4:32

variable to get a reference to the array element at that index. 4:36

_items, and then a pair of brackets, and 4:40

then inside of the brackets, the index local loop variable. 4:44

And that completed my implementation for the DisplayItems method. 4:53

Then, back in the Program.cs file, I added a call to the DisplayItems method, 4:57

right after writing the number of items to the console. 5:04

Media library.DisplayItems();. 5:17

And I commented out the DetectMediaType method calls. 5:22

And removed the Display method calls. 5:30

And lastly, I compiled and ran my program. 5:36

And here's the expected output. 6:03

Now that we have a method to display all of the items in our MediaLibrary, let's 6:09

improve our program yet again, by adding another method to the MediaLibrary class. 6:13

For the second challenge, add a method named, 6:19

FindItem to the MediaLibrary class that returns a media type item and 6:22

defines parameter of type string, named criteria. 6:26

Within the method body, use a for 6:30

each to loop throw the items array contained within the MediaLibrary class. 6:33

And return the item whose Title property contains the provided criteria string 6:39

parameter value, item, and defines a parameter of type string, named criteria. 6:44

If you need a hint on how to check if a string value contains another 6:52

string value, see the teacher's notes for 6:56

a walk-through of one way to solve this problem. 6:59

Then in the Program.cs file, test your work by searching the MediaLibrary for 7:02

an item by calling the FindItem method. 7:08

If an item is found, 7:11

pass it into a call to the static MediaLibrary DisplayItem method. 7:12

And if the item isn't found, write the message, "Item not found!" to the console. 7:18

And that's the second challenge. 7:24

See you in just a bit. 7:26

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