Driv4r

using Xamarin.Forms;

namespace Myproject.Views
{
    public class CustomView : View
    {
        public CustomView()
        {
        }
    }

Driv4r

using Myproject.Interfaces;
using Myproject.Pages;
using System;
using Xamarin.Forms;

namespace Myproject
{
    /// <summary>
    /// The main class that is used to initialze xamarin forms.
    /// </summary>
    public partial class App : Application
    {
        /// <summary>
        /// Gets or sets the UserPreferencesStore.
        /// </summary>
        public static IUserPreferencesStore UserPreferencesStore { get; private set; }

        public App(IUserPreferencesStore userPreferencesStore)
        {
            InitializeComponent();
            //Usually uses an init method, but this allows earlier access.
            App.UserPreferencesStore = userPreferencesStore;
            //App.Current.MainPage = new NavigationPage(new MainPage());
        }
    }
}

Driv4r

//Without sending arguments

//Subscribe
MessagingCenter.Subscribe<object> (this, "Arrived", (sender) => {
    // do something whenever the "Arrived" message is sent from whatever type 
    //<object> is.
});

//Send
//All subscribers to "Arrived" of type "this" will be notified.

Driv4r

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="Myproject.Pages.LoginPage"
             Padding="25, 20, 25, 10"
             BackgroundColor="{StaticResource defaultBackgroundColor}"
             Title="Sign In">
  <ContentPage.Content>
    <StackLayout Padding="10,0,10,20" VerticalOptions="FillAndExpand">
      <StackLayout x:Name="contentLayout" VerticalOptions="CenterAndExpand">
        <Image  Source="PPP_Logo.png"/>
        <Label Text="Email" TextColor="{StaticResource defaultLabelTextColor}" />
        <Entry x:Name="emailEntry" />
        <Label Text="Password" TextColor="{StaticResource defaultLabelTextColor}" />
        <Entry x:Name="passwordEntry" IsPassword="true"/>
        <Button Text="Sign In" TextColor="{StaticResource defaultButtonTextColor}"
        Clicked="OnLoginButtonClicked" BackgroundColor="{StaticResource greenButtonBackgroundColor}"/>