The default parameter value provided by the installer is right, but the code above was not the right code to get to the parameter.
For my WPF app, I had to go into the code behind for app.xaml. Override the OnStartUp and you have the parameter in an args property.
public String LoadedFileName = "";
protected override void OnStartup(StartupEventArgs e)
{
if (e.Args != null && e.Args.Length == 1)
{
String fileName = e.Args[0];
if (!String.IsNullOrEmpty(fileName))
LoadedFileName = fileName;
}
}
Then in the code for main window you cast Application.Current as the appropriate class so you can look at the LoadedFileName