WPF: Textbox and Binding to Double not able to type . on it

<Window x:Class="WpfApplication4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:l="clr-namespace:WpfApplication4"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <l:MyData x:Key="data" />
    </Window.Resources>

    <Grid DataContext="{StaticResource ResourceKey=data}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="5"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

        <TextBox Text="{Binding Path=MyProperty, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top"></TextBox>

        <GridSplitter Grid.Column="1" Width="5" HorizontalAlignment="Stretch" Background="#FFFFFF" ResizeBehavior="PreviousAndNext"/>

        <TextBlock Grid.Column="2" Text="{Binding Path=MyProperty}" />

    </Grid>

</Window>




using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication4
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }

    public class MyData : INotifyPropertyChanged
    {
        private double myProperty;
        public double MyProperty { get { return myProperty; } set { myProperty = value; Notify("MyProperty"); } }

        private void Notify(string p)
        {
            if(PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(p));
        }

        public MyData()
        {
            MyProperty = 0;
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}