Erro BC30002 Type PrintWindow is not defined in WPF Application with VB.NET

Dear Sir,

I have an error `Erro BC30002 Type 'PrintWindow' is not defined ` in WPF Application with VB.NET

Please Guide me

Thanks

Imports System.IO
Imports System.Windows.Xps
Imports System.Windows.Xps.Packaging

Class MainWindow
    Public Property Document As FixedDocumentSequence
    Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
        If File.Exists("printPreview.xps") Then
            File.Delete("printPreview.xps")
        End If
        Dim xpsDocument As New XpsDocument("printPreview.xps", FileAccess.ReadWrite)
        Dim writer As XpsDocumentWriter = XpsDocument.CreateXpsDocumentWriter(xpsDocument)
        writer.Write(DirectCast(FD, IDocumentPaginatorSource).DocumentPaginator)
        Document = xpsDocument.GetFixedDocumentSequence()
        xpsDocument.Close()
'error below line code
        Dim windows = New PrintWindow(Document)
        windows.ShowDialog()

    End Sub
End Class