Example of how implement share text and links in Xamarin.Forms applications. - http://julianocustodio.com/share-xamarin-forms

MainPage.xaml.cs

using Plugin.Share;
using System;
using Xamarin.Forms;

namespace ShareDemo
{
	public partial class MainPage : ContentPage
	{
		public MainPage()
		{
		    InitializeComponent();
		}

		private void Share_Tapped(object sender, EventArgs e)
		{
		    var ShareMessage = new Plugin.Share.Abstractions.ShareMessage
		    {
			Text = "Exemplo de como compartilhar textos ou links em Aplicações Xamarin.Forms. / Example of how to share texts or links in Xamarin.Forms Applications.",
			Title = "Share",
			Url = "https://www.julianocustodio.com"
		    };

		    CrossShare.Current.Share(ShareMessage);
		}
    	}
}