Event Handler Null

Event Handler Null

In the MainWindow() I register an event handler
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
pageViewDocText = new PageViewDocText();
framePageDocFieldDetail.Content = pageViewDocText;
pageViewDocText.NewPageIRPRO += new
GabeLib.SearchCls.DocEventHandler(ViewIPRO);
}
protected void ViewIPRO(string IRPOlink)
public partial class PageViewDocText : Page, INotifyPropertyChanged
{
public event GabeLib.SearchCls.DocEventHandler NewPageIRPRO;
But in PageViewDocText NewPageIRPRO is null
What am I doing wrong?
From PageViewDocText I want to call MainWindow.ViewIPRO