using System;
using System.Collections.Generic;
using System.Text;

namespace MVVMBinding.Models
{
    public class Employee
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string FullName
        {
            get { return string.Format("{0} {1}", FirstName, LastName); }
        }
    }
}

using MVVMBinding.Models;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Text;

namespace MVVMBinding.ViewModels
{
    public class EmployeeVM : INotifyPropertyChanged
    {
        private ObservableCollection<Employee> _employees;
        public ObservableCollection<Employee> Employees {
            get
            {
                return this._employees;
            }
            set
            {
                this._employees = value;
                OnPropertyChanged();
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(
        [CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this,
            new PropertyChangedEventArgs(propertyName));
        }

        public EmployeeVM()
        {
            Employees = new ObservableCollection<Employee>();
        }

        public void AddNewEmployee(string fisrtName,string lastName)
        {
            Employee emp = new Employee()
            {
                FirstName = fisrtName,
                LastName = lastName
            };
            Employees.Add(emp);
        }
    }
}

<?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="MVVMBinding.Views.EmployeePage">
    <ContentPage.Content>
        <StackLayout>
            <Label Text="My Employee"
                VerticalOptions="CenterAndExpand" 
                HorizontalOptions="CenterAndExpand" />
            <StackLayout>
                <Label Text="ชื่อ"/>
                <Entry Placeholder="กรอกชื่อ" x:Name="fnameEntry"/>
                <Label Text="นามสกุล"/>
                <Entry Placeholder="กรอกนามสกุล" x:Name="lnameEntry"/>
                <Button x:Name="addBtn" Text="Add" Clicked="AddBtn_Clicked" />
                <ListView ItemsSource="{Binding Employees}" BackgroundColor="Beige">
                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <ViewCell>
                                <Label Text="{Binding FullName}"/>
                            </ViewCell>
                        </DataTemplate>
                    </ListView.ItemTemplate>
                </ListView>
            </StackLayout>
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

using MVVMBinding.ViewModels;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace MVVMBinding.Views
{
	[XamlCompilation(XamlCompilationOptions.Compile)]
	public partial class EmployeePage : ContentPage
	{
        private EmployeeVM vm;
        public EmployeePage ()
		{
			InitializeComponent ();
            vm = new EmployeeVM();
            this.BindingContext = vm;
		}

        private void AddBtn_Clicked(object sender, EventArgs e)
        {
            vm.AddNewEmployee(fnameEntry.Text, lnameEntry.Text);
            ClearEntry();
        }
        private void ClearEntry()
        {
            fnameEntry.Text = "";
            lnameEntry.Text = "";
        }
    }
}

using MVVMBinding.Views;
using System;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

[assembly: XamlCompilation(XamlCompilationOptions.Compile)]
namespace MVVMBinding
{
    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();

            MainPage = new EmployeePage();
        }

        protected override void OnStart()
        {
            // Handle when your app starts
        }

        protected override void OnSleep()
        {
            // Handle when your app sleeps
        }

        protected override void OnResume()
        {
            // Handle when your app resumes
        }
    }
}