Accessing a Winform from a WPF user control

I'm trying to access a winform from the wpf usercontrol that is sitting on it. I realize that there is an ElemetHost that is automatically created when you drop a WPF usercontrol onto a winform but I'm not sure how to get something simple to work. For instance: If I have a button on the WPF control, how could I get it to close the winform that the usercontrol is sitting on?

Thanks

Form1 Loaded

this.elementHost1.Child = new UserControl1() { Tag = this };

XAML of WpfUserControl

<UserControl x:Class="WindowsFormsApp7.UserControl1"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WindowsFormsApp7"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
    <Grid Background="DarkSlateGray">
        <Button Name="btnClose" Width="100" Height="25" Content="Close" Click="BtnClose_Click" />
    </Grid>
</UserControl>

btnClose Click of WpfUserControl

private void BtnClose_Click(object sender, RoutedEventArgs e)
{
    Form1 form = (Form1)this.Tag;
    form.Close();
}

Use Tag property of WPFUserControl as a refence holder.