App.cs

using Xamarin.Forms;

namespace AppForms
{
    public class App : Application
    {
        public App()
        {
            MainPage = new MasterDetailPage
            {
                Title = "Demo",
                Detail = new ContentPage
                {
                    Content = new StackLayout
                    {
                        VerticalOptions = LayoutOptions.Center,
                        Children =
                        {
                            new Label
                            {
                                HorizontalTextAlignment = TextAlignment.Center,
                                Text = "Hola mundo desde Xamarin Forms!",
                                FontSize = 30
                            }
                        }
                    }
                },
                Master = new ContentPage
                {
                    Title = "Demo App",
                    Content = new StackLayout
                    {
                        BackgroundColor = Color.Yellow,
                        Children =
                        {
                            new Label
                            {
                                HorizontalTextAlignment= TextAlignment.Center,
                                Text = "Menú lateral",
                                FontSize = 26,
                                TextColor = Color.Black
                            }
                        }
                    }
                }
            };
        }
    }
}