How did you with the second challenge?

Let's walk through my solution.

In the program.cs file main method,

I used the new keyword to create an instance of each of my media type classes.

First a variable, var album

= new Album with a capital A followed by a set of parentheses.

Then var book = new Book.

Then var movie = new Movie.

Then I set each object field to a value.

First the album.

So album.Title = and

then how about Yellow Submarine?

Then album.artist = "The Beatles".

For the book, how about

book.title = Moby Dick and

book.author equals Herman Melville.

And for the movie,

movie.Title = Lawrence of Arabia and

movie.Director = David Lean and

lastly I compiled my program.

View, Show Console,

mcs *.cs-out:Program.exe.

Now let's try running the program.

So mono Program.exe and

nothing happened.

Let's take another look at our code.

So here's our static void main method.

That's the method that's getting called when we ran our application, but notice

that I instantiated each of my media type classes, and then I set field values.

But I didn't do anything, I didn't write anything to the console.

Let's fix that.

For now, let's just write each object's field values to the console.

So console.WriteLine, then for

the value I'll start with a string literal,

album: " + plus album.title

+ " by " + album.Artist);

let's repeat that again for

both the book and the movie.

To save some typing I'll copy and paste.

Change Album to Book and then Album here to book and

then instead of album.Artists it's book.Author.

And then instead of album

it's Movie Movie.title by

movie.Director.

Now let's compile and run the program again.

This time, I'll run both commands at the same time.

So, ncs*.cs -out: Program.exe

&& mono Program.exe.

And this time, we got our media type information written to the console.

Great work.

Let's review how we're setting our field values.

Currently, we're creating a class instance, then writing a line of code for

each field value that we want to set.

As we've seen, this works fine but

if we had a lot of fields, this approach could become tedious.

Furthermore, when thinking about these media types, setting a value for

each of these fields doesn't really feel optional.

Though, with our current approach,

it's perfectly valid at least as far as the C# compiler's concern to create

an instance of any of these media types, and not set any of the field values.

To fix this, we can add a constructor to each of our media type classes,

each constructor can define a parameter for

each field that should have a value, the required fields for that media type.

For example, here in my album class, I'll add a constructor with title and

artist parameters and then use those parameters to initialize these fields.

For the third and last challenge in this practice session,

add a constructor to each of your media type classes.

Define a parameter for each of the required fields and

use those parameter values to initialize the fields.

After adding your class constructors, you'll need to update the code

in the Program.cs file 'Main()' method in order for

your program to successfully compile.

And that's it for the third challenge.

See you in a bit.