Is this ShowDialog tip valid or obsolete?

I am going through the confusion (aka learning curve) about:

using Microsoft.Win32;
         vs.
using System.Windows.Forms;

and Forms vs. WPF, so please bear with me.

Is the tip described here valid?

     http://www.codeproject.com/Tips/87317/TIP-Handling-WPF-DialogResult-with-simplicity

The reason I ask is because I cannot make it work.