Adding the App.xaml and the App.xaml.cs

Create a new Xamarin.Forms Content Page item into the MvvmCross.Forms.UI project. Notice that do not select the other file items, as shown below:

Open this file and replace the content with the below codes:

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="MvvmCrossDemo.Forms.UI.App">
    <Application.Resources>
    </Application.Resources>
</Application>

You can find the sample code here: https://github.com/MvvmCross/MvvmCross/blob/develop/ContentFiles/Forms/FormsUIContent/App.xaml.pp.

Open the App.xaml.cs file and update the content. The default base class of the App class is ContentPage, and we need to change it to inherit from the Xamarin.Forms.Application class, like this:

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace MvvmCrossDemo.Forms.UI
{
    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();
        }
    }
}

You can find the sample code here: https://github.com/MvvmCross/MvvmCross/blob/develop/ContentFiles/Forms/FormsUIContent/App.xaml.cs.pp.