keep getting System.IO.FileNotFoundException: Could not load file or assembly ‘mysharedproject'

I have created sharedproject solution and my IOS project is pointing to the XAML file in my share project but I am having dificulties . why when I remove the xamarin.forms.Application from the base class , my IOS cannot find it

using System;
using System.Collections.Generic;
using System.Linq;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace mysharedproject.Mobile
{
    //[XamlCompilation (XamlCompilationOptions.Skip)]
    public partial class App : Application
    {
        public static DateTime MinimumDate = DateTime.Parse("Jan 1 2000");
        public static DateTime MaximumDate = DateTime.Parse("Dec 31 2050");
        public static MasterDetailPage MasterDetailPage;
        public App ()
        {
            InitializeComponent ();
            MainPage = GetMainPage();
            MainPage.SetValue (NavigationPage.BarTextColorProperty, Color.White);
        }

        public static Page GetMainPage()
        {
            return new RootPage(true);
        }
    }
}

I have already added xamarin.forms into my IOS

project

but when I put back the xamarin.form.application back to my file then once I build the IOS app it says System.IO.FileNotFoundException: Could not load file or assembly ‘mysharedproject' or one of its dependencies