WPF MVVM simple code did`t Working

[sanjay.vaniya]

my snippet code:

User.cs in model folder

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel;

namespace WpfApp7.Model
{
    public class User : INotifyPropertyChanged
    {
        private int userId;
        private string firstName;
        private string lastName;
        private string city;
        private string state;
        private string country;
        public int UserId
        {
            get
            {
                return userId;
            }
            set
            {
                userId = value;
                OnPropertyChanged("UserId");
            }
        }
        public string FirstName
        {
            get
            {
                return firstName;
            }
            set
            {
                firstName = value;
                OnPropertyChanged("FirstName");
            }
        }
        public string LastName
        {
            get
            {
                return lastName;
            }
            set
            {
                lastName = value;
                OnPropertyChanged("LastName");
            }
        }
        public string City
        {
            get
            {
                return city;
            }
            set
            {
                city = value;
                OnPropertyChanged("City");
            }
        }
        public string State
        {
            get
            {
                return state;
            }
            set
            {
                state = value;
                OnPropertyChanged("State");
            }
        }
        public string Country
        {
            get
            {
                return country;
            }
            set
            {
                country = value;
                OnPropertyChanged("Country");
            }
        }

        #region INotifyPropertyChanged Members  

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion

    }
}

UserViewModel.cs on ViewModel folder

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

namespace WpfApp7.ViewModel
{
    using System.Windows.Input;
    using System.ComponentModel;
    using WpfApp7.Model;

    class UserViewModel
    {
        private IList<User> _UsersList;

        public UserViewModel()
        {
            _UsersList = new List<User>
            {
                new User{UserId = 1,FirstName="Raj",LastName="Beniwal",City="Delhi",State="DEL",Country="INDIA"},
                new User{UserId=2,FirstName="Mark",LastName="henry",City="New York", State="NY", Country="USA"},
                new User{UserId=3,FirstName="Mahesh",LastName="Chand",City="Philadelphia", State="PHL", Country="USA"},
                new User{UserId=4,FirstName="Vikash",LastName="Nanda",City="Noida", State="UP", Country="INDIA"},
                new User{UserId=5,FirstName="Harsh",LastName="Kumar",City="Ghaziabad", State="UP", Country="INDIA"},
                new User{UserId=6,FirstName="Reetesh",LastName="Tomar",City="Mumbai", State="MP", Country="INDIA"},
                new User{UserId=7,FirstName="Deven",LastName="Verma",City="Palwal", State="HP", Country="INDIA"},
                new User{UserId=8,FirstName="Ravi",LastName="Taneja",City="Delhi", State="DEL", Country="INDIA"}
            };
        }

        public IList<User> Users
        {
            get { return _UsersList; }
            set { _UsersList = value; }
        }

        private ICommand mUpdater;
        public ICommand UpdateCommand
        {
            get
            {
                if (mUpdater == null)
                    mUpdater = new Updater();
                return mUpdater;
            }
            set
            {
                mUpdater = value;
            }
        }

        private class Updater : ICommand
        {
            #region ICommand Members  

            public bool CanExecute(object parameter)
            {
                return true;
            }

            public event EventHandler CanExecuteChanged;

            public void Execute(object parameter)
            {

            }

            #endregion
        }
    }
}

MainPage.xaml in View folder

<Window x:Class="WpfApp7.View.MainPage"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp7.View"
        mc:Ignorable="d"
        Title="MainPage" Height="485" Width="525">
    <Grid Margin="0,0,0,20">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <ListView Name="UserGrid" Grid.Row="1" Margin="4,178,12,13"  ItemsSource="{Binding Users}"  >
            <ListView.View>
                <GridView x:Name="grdTest">
                    <GridViewColumn Header="UserId" DisplayMemberBinding="{Binding UserId}"  Width="50"/>
                    <GridViewColumn Header="First Name" DisplayMemberBinding="{Binding FirstName}"  Width="80" />
                    <GridViewColumn Header="Last Name" DisplayMemberBinding="{Binding LastName}" Width="100" />
                    <GridViewColumn Header="City" DisplayMemberBinding="{Binding City}" Width="80" />
                    <GridViewColumn Header="State" DisplayMemberBinding="{Binding State}" Width="80" />
                    <GridViewColumn Header="Country" DisplayMemberBinding="{Binding Country}" Width="100" />
                </GridView>
            </ListView.View>
        </ListView>
        <TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,7,0,0" Name="txtUserId" VerticalAlignment="Top" Width="178" Text="{Binding ElementName=UserGrid,Path=SelectedItem.UserId}" />
        <TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,35,0,0" Name="txtFirstName" VerticalAlignment="Top" Width="178" Text="{Binding ElementName=UserGrid,Path=SelectedItem.FirstName}" />
        <TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,62,0,0" Name="txtLastName" VerticalAlignment="Top" Width="178" Text="{Binding ElementName=UserGrid,Path=SelectedItem.LastName}" />
        <Label Content="UserId" Grid.Row="1" HorizontalAlignment="Left" Margin="12,12,0,274" Name="label1" />
        <Label Content="Last Name" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,60,0,0" Name="label2" VerticalAlignment="Top" />
        <Label Content="First Name" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,35,0,0" Name="label3" VerticalAlignment="Top" />
        <Button Content="Update" Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="310,40,0,0" Name="btnUpdate"   
                VerticalAlignment="Top" Width="141"  
                Command="{Binding Path=UpdateCommad}" Click="btnUpdate_Click"  />
        <TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,143,0,0" x:Name="txtCity" VerticalAlignment="Top" Width="178" Text="{Binding SelectedItem.City, ElementName=UserGrid}" />
        <Label Content="Country" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,141,0,0" x:Name="label2_Copy" VerticalAlignment="Top" />
        <TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,88,0,0" x:Name="txtCountry" VerticalAlignment="Top" Width="178" Text="{Binding SelectedItem.Country, ElementName=UserGrid}" />
        <Label Content="City" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,86,0,0" x:Name="label2_Copy1" VerticalAlignment="Top" />
        <TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,115,0,0" x:Name="txtSTate" VerticalAlignment="Top" Width="178" Text="{Binding SelectedItem.State, ElementName=UserGrid}" />
        <Label Content="State" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,113,0,0" x:Name="label2_Copy2" VerticalAlignment="Top" />
    </Grid>
</Window>

App.xaml.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
using WpfApp7.ViewModel;

namespace WpfApp7
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            WpfApp7.MainWindow window = new MainWindow();
            UserViewModel VM = new UserViewModel();
            window.DataContext = VM;
            window.Show();
        }
    }
}