# Generics vs Non-Generics

# Non-Generics

We are going to create an ArrayList which is Non-Generic.

Let's create an array variable to which we add all sorts of items:

var array = new ArrayList
{
    21,
    "computer",
    true
};

But what about adding an object?

For this example, we need to create a custom class called Song.

Firstly, let's create a variable called song:

var song = new Song()
{
    Artist = "twenty one pilots",
    Name = "Lane Boy"
};

Then, hover over the Song class, press Ctrl + ., and then choose to Generate Class Song.

This will generate the following code:

internal class Song
{
    public Song()
    {
    }

    public string Artist { get; set; }
    public string Name { get; set; }
}

And we can add it to the array.

array.Add(song);

Let's print the values of the array:

foreach (var item in array)
{
    Console.WriteLine(item);
}

# Limitations

Now this works, but what about printing the Name property of the song?

If we do the casting directly, the program will crash when the item is not a Song:

foreach (var item in array)
{
    Console.WriteLine(((Song)item).Name);
}

To fix this, we can check to see if the current item is a Song object and then we can try to print its Name property.

foreach (var item in array)
{
    if (item is Song)
    {
        Console.WriteLine(((Song)item).Name);
    }
}

We can do this with the as operator as well, but we need to introduce a new variable:

foreach (var item in array)
{
    if (item is Song)
    {
        var songItem = item as Song;
        Console.WriteLine(songItem.Name);
    }
}

So, you can see how difficult it became to operate on individual items.

Indeed, we have flexibility to add any item we want, but in the long run it's not maintainable. This code is prone to errors.

# Generics

This is where we have Generics.

Let's create a list of type Song.

var list = new List<Song>();

To this list, we can add only Song objects:

var list = new List<Song>
{
    //21, // error
    song
};

Let's get the Name property of the song directly without casting:

foreach (var item in list)
{
    Console.WriteLine(item.Name);
}

# Conclusion

This is the power of Generics.