close wpf user control in VB.net

Question

Hi Everyone
I'm stuck on this issue, please help.

I created an user control named "CreateNewCase_uc" within which  I created a button Close named "btnClose"

In my MainWindow, I created a Grid named "grid1" and a button Open named "btnCreateNewCase" with this code

Private Sub btnCreateNewCase_Click(sender As Object, e As RoutedEventArgs)
 
        Dim cnc As CreateNewCase_uc = New CreateNewCase_uc
        grid1.Children.Clear()
        grid1.Children.Add(cnc)
    End Sub

My question : which Code I need to Write for my bntClose button which is inside the user control to close or make disappeared the user control in VB.NET

Thanks in advance for your help.