Bummer! This is just a preview. You need to be signed in with a Basic account to view the entire video.

Preview

Start a free Basic trial
to watch this video

Sign up for Treehouse

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.

Instructions

2nd Challenge

  1. 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.

  2. 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.

  • 0:00

    Welcome back!

  • 0:00

    How did you do?

  • 0:01

    Let's walk through my solution.

  • 0:03

    In the MediaLibrary class,

  • 0:08

    I stubbed out a method named,

  • 0:14

    DisplayItems.

  • 0:24

    Within the method body, I added a for loop.

  • 0:33

    Remember that a for loop has three sections,

  • 0:36

    the initializer, the condition and the iterator sections.

  • 0:41

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

  • 0:47

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

  • 0:56

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

  • 1:01

    currently accessing within the loop.

  • 1:03

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

  • 1:08

    I use the expression index

  • 1:13

    < _items.Length.

  • 1:22

    This expression will be evaluated right before each loop iteration.

  • 1:26

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

  • 1:32

    will be asked.

  • 1:33

    If yes, then the loop iteration is executed,

  • 1:37

    otherwise the loop will be exited.

  • 1:40

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

  • 1:44

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

  • 1:50

    The ++ operator, or the increment operator,

  • 1:55

    increments or increases the operand or variable by one.

  • 2:01

    After defining the initializer, condition, and iterator sections for

  • 2:06

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

  • 2:11

    To write each item's information to the console,

  • 2:14

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

  • 2:19

    But to get access to the display text property,

  • 2:22

    we first need to cast the item to its subtype.

  • 2:25

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

  • 2:29

    already does all of this.

  • 2:33

    In the Progam.cs file, the Display method

  • 2:37

    provides the behavior that we're looking for.

  • 2:43

    Given that, I decided to move the Display method

  • 2:48

    from the Program.cs file to the MediaLibray class.

  • 2:54

    I selected the method and cut it to the clipboard.

  • 3:00

    Then I switched back to the MediaLibrary class file,

  • 3:06

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

  • 3:18

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

  • 3:23

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

  • 3:27

    the Program.cs file Main method.

  • 3:29

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

  • 3:36

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

  • 3:44

    And I added a using directive for the system namespace.

  • 3:47

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

  • 4:00

    Actually, after adding this using directive,

  • 4:02

    we can also update our GetItemAt method.

  • 4:10

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

  • 4:22

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

  • 4:32

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

  • 4:36

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

  • 4:40

    _items, and then a pair of brackets, and

  • 4:44

    then inside of the brackets, the index local loop variable.

  • 4:53

    And that completed my implementation for the DisplayItems method.

  • 4:57

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

  • 5:04

    right after writing the number of items to the console.

  • 5:17

    Media library.DisplayItems();.

  • 5:22

    And I commented out the DetectMediaType method calls.

  • 5:30

    And removed the Display method calls.

  • 5:36

    And lastly, I compiled and ran my program.

  • 6:03

    And here's the expected output.

  • 6:09

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

  • 6:13

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

  • 6:19

    For the second challenge, add a method named,

  • 6:22

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

  • 6:26

    defines parameter of type string, named criteria.

  • 6:30

    Within the method body, use a for

  • 6:33

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

  • 6:39

    And return the item whose Title property contains the provided criteria string

  • 6:44

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

  • 6:52

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

  • 6:56

    string value, see the teacher's notes for

  • 6:59

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

  • 7:02

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

  • 7:08

    an item by calling the FindItem method.

  • 7:11

    If an item is found,

  • 7:12

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

  • 7:18

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

  • 7:24

    And that's the second challenge.

  • 7:26

    See you in just a bit.

You need to sign up for Treehouse in order to download course files.

Sign up