WPF binding a text box to and XElement

I have been binging this for hours and cannot find a sample that seems to work.  I have an XDocument.  The XML is structured like this...

<JBIndexData>
    <MSI>
        <Title>
            <Main>Main Title Goes Here</Main>
        </Title>
    </MSI>
</JBIndexData>

In my code getting the XElement for JBIndexData.  I am setting the forms DataContext = to the JBIndexData's XElement.  In my XAML i have a TextBox. 

<TextBox x:Name="txtMain1" Grid.Row="1" Grid.Column="1" Text="{Binding XPath=MSI/Title/Main, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

I am trying to bind it so it will display the "Main Title Goes Here" (Value of Main XElement).

How should my binding work for this?

Thanks, JLinker