С# MVVM WPF Добавление и удаление в DateGrid

View

    <Window x:Class="Person_Changed.MainWindow"
            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:Person_Changed"
            xmlns:human="clr-namespace:Person_Changed.ViewModel"
            mc:Ignorable="d"
            Title="MainWindow" Height="355.263" Width="493.421">
        <Window.DataContext>
            <human:HumanViewModel/>
        </Window.DataContext>
        <Grid Margin="0,0,2,-5">
            <ListView 
                x:Name="listView"
                ItemsSource="{Binding Humans }"
                Margin="10,122,10,10">
                <ListView.View>
                    <GridView>
                        <GridViewColumn Header="Ид"      DisplayMemberBinding="{Binding Id}"         Width="60" />
                        <GridViewColumn Header="Имя"     DisplayMemberBinding="{Binding FirstName}"  Width="70" />
                        <GridViewColumn Header="Фамилия" DisplayMemberBinding="{Binding SurName}"    Width="80" />
                        <GridViewColumn Header="Паспорт" DisplayMemberBinding="{Binding Passport}"   Width="100" />
                        <GridViewColumn Header="Дата"    DisplayMemberBinding="{Binding DataBirth}"  Width= "150" />
                    </GridView>
                </ListView.View>
            </ListView>
            <Button  
                Content="Добавить"
                HorizontalAlignment="Left"
                Margin="161,0,0,283"
                Width="84"
                Command="{Binding AddHuman}"
                BorderThickness="0" Height="36" VerticalAlignment="Bottom"/>
            <TextBox  HorizontalAlignment="Left" Height="20" Text="{Binding FirstName,  UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top" Width="120" Margin="10,10,0,0"/>
            <TextBox  HorizontalAlignment="Left" Height="20" Text="{Binding SurName,    UpdateSourceTrigger=PropertyChanged}"   VerticalAlignment="Top" Width="120" Margin="10,38,0,0"/>
            <TextBox  HorizontalAlignment="Left" Height="20" Text="{Binding Passport,   UpdateSourceTrigger=PropertyChanged}"  VerticalAlignment="Top" Width="120" Margin="10,66,0,0"/>
            <DatePicker HorizontalAlignment="Left" Height="20" Text="{Binding DataBirth,   UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top" Margin="10,93,0,0" Width="120" FontSize="10" FontFamily="Times New Roman"/>
            <Button  
                Content="Удалить"
                HorizontalAlignment="Left"
                Margin="161,0,0,230"
                Width="84"
                BorderThickness="0" Height="36" VerticalAlignment="Bottom"/>

        </Grid>
    </Window>

Human

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using GalaSoft.MvvmLight;
namespace Person_Changed.Model
{
    public class Human : ObservableObject
    {
        private int _id;
        private string _firstname;
        private string _surname;
        private string _passport;
        private DateTime _databirth;

        #region property
        public int Id
        {
            get { return _id; }
            set
            {
                _id = value;
                RaisePropertyChanged(() => Id);
            }
        }
        public string FirstName
        {
            get { return _firstname; }
            set
            {
                _firstname = value;
                RaisePropertyChanged(() => FirstName);
            }
        }
        public string SurName
        {
            get { return _surname; }
            set
            {
                _surname = value;
                RaisePropertyChanged(() => SurName);
            }
        }
        public string Passport
        {
            get { return _passport; }
            set
            {
                _passport = value;
                RaisePropertyChanged(() => Passport);
            }
        }
        //[DisplayFormat(DataFormatString ="{0:dd'/'MM'/'yyyy}",ApplyFormatInEditMode =true)]
        public DateTime DataBirth
        {
            get { return _databirth; }
            set
            {
                _databirth = value;
                RaisePropertyChanged(() => DataBirth);
            }
        }
        #endregion
    }
}

HumanViewModel

using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using Person_Changed.Model;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
namespace Person_Changed.ViewModel
{
    class HumanViewModel : ViewModelBase
    {
        public ObservableCollection<Human> Humans { get; set; }
        private Human _selectedhuman;
        public Human SelectedHuman
        {
            get { return _selectedhuman; }
            set
            {
                _selectedhuman = value;
                RaisePropertyChanged(() => SelectedHuman);
            }
        }
        public HumanViewModel()
        {
            DateTime newdate = new DateTime(2018, 01, 01);
            Humans = new ObservableCollection<Human>
            {
                new Human {Id = 1, FirstName="Иван", SurName = "Иванов", Passport = "1111-111111", DataBirth = newdate}
            };
        }
        private ICommand _addhuman;
        public ICommand AddHuman
        {
            get
            {
                return _addhuman ?? (_addhuman = new RelayCommand(() => 
                {
                    Human human = new Human();
                    Humans.Add(human);
                }));
            }
        }
    }
}

Цель - Добавить значение в коллекцию DataGrid из textbox'ов

У меня почему-то не перехватывается биндинги полей и заполняется нулями