EventAggregato

MainViewModel.cs

using System;
using System.Threading.Tasks;
using MvvmHelpers;
using MvvmHelpers.Commands;
using Xamarin.Forms;
using XamarinFormsEventAggregator.Events;

namespace XamarinFormsEventAggregator.ViewModels
{
    public class MainViewModel : BaseViewModel
    {
        private readonly IEventAggregator _EventAggregator;
        public MvvmHelpers.Commands.Command SomarViewCommand { get; }

        string _texto;
        public string Texto
        {
            get
            {
                return _texto;
            }
            set
            {
                SetProperty(ref _texto, value);
            }
        }


        public MainViewModel(IEventAggregator eventAggregator)
        {
            _texto = "Soma 0";
            _EventAggregator = eventAggregator;

            //Registra o Evento
            EventAggregator.Instance.RegisterHandler<SomarMessage>(
       SomarHandler);

            SomarViewCommand = new MvvmHelpers.Commands.Command(async () => await SomarViewCommandExecute());
        }

        

        private void SomarHandler(
    SomarMessage message)
        {
            Texto = message.Texto;
        }


        private async Task SomarViewCommandExecute()
        {
            await Xamarin.Forms.Application.Current.
               MainPage.Navigation.PushAsync(new SomarPage());
        }
    }
}