WPF Datepicker Control

I have a datepicker, but it is allowing me to enter any text. I want to disable user from entering text. User should be allowed to select date from the calendar. 

<Window x:Class="MyTestForDatePicker.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <!--<Grid>-->
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="auto"></ColumnDefinition>
                <ColumnDefinition></ColumnDefinition>
                <ColumnDefinition Width="auto"></ColumnDefinition>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition></RowDefinition>
            </Grid.RowDefinitions>
            <DatePicker Grid.Column="0" Grid.Row="0" Margin="2" Name="MySelectedDate" VerticalContentAlignment="Center" ></DatePicker>
        <DatePickerTextBox Grid.Column="1" Grid.Row="3" Margin="2" Name="SelectedDate" IsReadOnly="True"></DatePickerTextBox>
        <Button Grid.Column="1" Grid.Row="1" Margin="100,102,203,154" VerticalContentAlignment="Center" Name="Ok" Click="Ok_Click_1"/>
    </Grid>
</Window>