gistfile1.txt

    public class DummyVm : INotifyPropertyChanged
    {
        public DummyVm()
        {
            this.Items= new ObservableCollection<DummyItem>(new List<DummyItem>
                {
                    new DummyItem(){Name = "Maverick", Country = "England"},
                    new DummyItem(){Name = "Johan", Country = "SwedenLand"},
                    new DummyItem(){Name = "Gregory", Country = "England"},
                    new DummyItem(){Name = "Jackomel", Country = "Unknown"}
                });

            
        }

        public int CurrentIndex
        {
            get { return this._currentIndex; }
            set
            {
                if (value == this._currentIndex) return;
                this._currentIndex = value;
                this.OnPropertyChanged();
                this.OnPropertyChanged("Current");
            }
        }

        public DummyItem Current { get { return this.Items[this.CurrentIndex]; } }

        public ObservableCollection<DummyItem> Items { get; set; }
        private int _currentIndex;

        public event PropertyChangedEventHandler PropertyChanged;

        [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            var handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public class DummyItem
    {
        public string Name { get; set; }
        public string Country { get; set; }
    }

gistfile2.txt

<Window x:Class="WpfTextboxDummy.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:wpfTextboxDummy="clr-namespace:WpfTextboxDummy"
        xmlns:system="clr-namespace:System;assembly=mscorlib"
                xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        d:DataContext="{d:DesignInstance wpfTextboxDummy:DummyVm, IsDesignTimeCreatable=True}"
        Title="MainWindow" Height="350" Width="525">
    <DockPanel>
        <DataGrid ItemsSource="{Binding Items}" SelectedIndex="{Binding CurrentIndex}" DockPanel.Dock="Top"></DataGrid>
        <GroupBox Header="DetailView" DockPanel.Dock="Top">
            <StackPanel>
                <TextBox Text="{Binding Current.Name}"></TextBox>
                <TextBox Text="{Binding Current.Country}"></TextBox>
            </StackPanel>
        </GroupBox>
        <StackPanel Orientation="Horizontal">
            <Button Click="BackClick">Back</Button>
            <TextBox Text="{Binding CurrentIndex}"></TextBox>
            <Button Click="ForwardClick">Next</Button>
        </StackPanel>
    </DockPanel>

</Window>

gistfile3.txt

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = new DummyVm();
        }

        private void BackClick(object sender, RoutedEventArgs e)
        {
            var vm = (DummyVm)this.DataContext;
            if (vm.CurrentIndex > 0)
                vm.CurrentIndex--;
        }

        private void ForwardClick(object sender, RoutedEventArgs e)
        {
            var vm = (DummyVm)this.DataContext;
            if (vm.CurrentIndex < (vm.Items.Count()-1))
                vm.CurrentIndex++;
        }
    }