[CONNECT .NET] WPFInteropHelper

I'm writing a .NET AddIn that uses WPF for its user interface.  Borrowing from the WPF examples delivered with the SDK, I am able to display a XPF form.

The example uses class WPFInteropHelper.  WPFInteropHelper.IconName presumably does what it says on the tin, but I can't get it to work.  In the absence of documentation, I've tried different approaches.

WPFInteropHelper.IconName expects what:

1. The name of an icon?
2. The file title of an icon?
3. The file path of an icon?

Should the icon be:

1. A Windows .bmp
2. A Windows .ico
3. something else?

Does it look for the icon>

1. In a resource in the same assembly
2. In a file?

The example has this:

 m_wndHelper.IconName = "DesignModel";  

However, I can't see an icon name DesignModel in the app's resource.