How to properly expose Windows form object to other classes - wpf

Question

I have a basic question. I'm creating a VSTO Word Addin. I have a Ribbon button which opens a WPF dialog box called TableSelector. It is hosted in a Windows form.
Public Class RibbonControl
Private f As Form
Private Sub btnSelectTable_Click(sender As Object, e As RibbonControlEventArgs) Handles btnSelectTable.Click
Dim h As New System.Windows.Forms.Integration.ElementHost()
Dim tableselector1 As New TableSelector
f = New Form()
f.MaximumSize = New Size(500, 380)
f.MinimumSize = New Size(500, 380)
f.MaximizeBox = False
f.Name = "HostForm"
h.Dock = DockStyle.Fill
h.Child = tableselector1
f.Controls.Add(h)
f.Show()
f.TopMost = True
End Sub
Public ReadOnly Property hostForm() As Form
Get
Return f
End Get
End Property
End Class
Then I have a close button on that WPF control to close the dialog box. When I click it I get runtime error "Object reference not set to an instance of an object." on line 3 of the below code.
Private Sub btnClose_Click(sender As Object, e As RoutedEventArgs) Handles btnClose.Click
Dim ribbon As New RibbonControl()
ribbon.hostForm.Close()
End Sub
What am I missing?

Answer 1

You can use following code for get the specific window for close
Window win = Application.Current.Windows.OfType<Window>().SingleOrDefault(w => w.Name == "Window Name");
win.Close();