reactiveui bind

// MainWindow.xaml.cs

using System.Windows;
using ReactiveUI;

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, IViewFor<string>
    {
        public MainWindow()
        {
            InitializeComponent();

            this.Bind(this, v => v.DataContext, v => v.ViewModel);
        }

        object IViewFor.ViewModel
        {
            get { return ViewModel; }
            set { ViewModel = (string) value; }
        }

        public static readonly DependencyProperty ViewModelProperty = DependencyProperty.Register(
            "ViewModel", typeof (string), typeof (MainWindow));

        public string ViewModel
        {
            get { return (string) GetValue(ViewModelProperty); }
            set { SetValue(ViewModelProperty, value); }
        }

        private int i;

        private void SetViewModel_Click(object sender, RoutedEventArgs e)
        {
            i++;
            ViewModel = i.ToString();
        }

        private void SetDataContext_Click(object sender, RoutedEventArgs e)
        {
            i++;
            DataContext = i.ToString();
        }
    }
}


// MainWindow.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Height="350" Width="525"
        >
    <!-- DataContext="{Binding RelativeSource={RelativeSource Self}, Path=ViewModel, Mode=TwoWay}" -->
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>

        <Button Grid.Row="0" Click="SetViewModel_Click" x:Name="btnViewModel">
            <TextBlock>
                <Run>Set ViewModel. CurrentValue: </Run><Run Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=Window}, Path=ViewModel}" />
            </TextBlock>
        </Button>
        <Button Grid.Row="1" Click="SetDataContext_Click" x:Name="btnDataContext">
            <TextBlock>
                <Run>Set DataContext. CurrentValue: </Run><Run Text="{Binding Mode=OneWay}" />
            </TextBlock>
        </Button>
    </Grid>
</Window>