DoToo

This is the .NET Standard library that all the platform-specific projects reference and the location to which most of our code will be added. The following screenshot displays the structure of the .NET Standard library:

Under Dependencies, we will find references to external dependencies such as Xamarin.Forms. We will update the Xamarin.Forms package version in the Updating Xamarin.Forms packages section. We will add more dependencies as we progress throughout the chapter.

The App.xaml file is a XAML file that represents the app. This is a good place to put application-wide resources, which we will do later on. We can also see the App.xaml.cs file, which contains the startup code and some lifetime events to which we can add custom code, such as OnStart or OnSleep.

If we open up App.xaml.cs, we can see the starting point for our Xamarin.Forms application:

public partial class App : Application
{
    public App()
    {
        InitializeComponent();
        MainPage = new DoToo.MainPage();
    }

    protected override void OnStart()
    {
        // Handle when your app starts
    }

    // code omitted for brevity
}

The assignment of a page to the MainPage property is particularly important, as this is what determines which page will be displayed to the user first. In the template, this is the DoToo.MainPage() class.

The last two files are the MainPage.xaml file, which contains the first page of the application and the code-behind file, which is called MainPage.xaml.cs. These files will be removed in order to comply with the Model–View–ViewModel (MVVM) naming standards.