Manipulate visibility by using x:Name=" as string from code - wpf

Question

Is it possible to manipulate visibility and other options of element by using x:Name=" as string in VB.Net + WPF?
Things i tried?
Dim w As MainWindow = Application.Current.Windows(0)
'Dim nameOfControl As String = ("buttonClose")
w.[nameOfControl].Visibility = Visibility.Visible
And outpus is as i expected it to be, nameOfControl is not memeber of main window
My final result should be to manipulate(visualy) all gui elements based on database information.

Answer 1

(Turns out OP needs to look up arbitrary controls by string name in a loop -- which is ideally done via MVVM and a redesign, but for now the answer is walking the visual tree).
You've already pretty much got it.
Dim w As MainWindow = Application.Current.Windows(0)
w.buttonClose.Visibility = Visibility.Collapsed
When you put the x:Name attribute on a control, WPF gives the parent class (MainWindow in this case) a Friend property for the control that has that name. Friend (C# calls it internal) means any code in the same assembly has access to it. w is a reference to your MainWindow class, so there it is.
Therefore, assuming this code is in the same assembly as MainWindow, that should work.

Answer 2

Edit2: Fixed a bug that caused only the first child of matching type to be returned.
Edit: After looking into this more, it seems there are some substantial differences with extension methods in C# and VB.Net. I have made some changes to hopefully account for those changes.
The following method will get all children of the given visual (Window is a Visual):
Imports System.Collections.Generic;
Imports System.Windows;
Imports System.Windows.Media;
Module VisualExtensions
<System.Runtime.CompilerServices.Extension>
Public Function GetVisualChildren(Of T As Visual)(parent As DependencyObject) As IEnumerable(Of T)
Dim child As T = Nothing
Dim numVisuals As Integer = VisualTreeHelper.GetChildrenCount(parent)
For i As Integer = 0 To numVisuals - 1
Dim v As Visual = DirectCast(VisualTreeHelper.GetChild(parent, i), Visual)
child = TryCast(v, T)
If v IsNot Nothing Then
For Each item As var In GetVisualChildren(Of T)(v)
yield Return item
Next
End If
If child IsNot Nothing Then
yield Return child
End If
Next
End Function
End Module
This extension method must be in a Module, like shown above.
You can get a child with a specific name like so:
Dim window = Application.Current.Windows(0)
Dim visuals = window.GetVisualChildren(Of FrameworkElement)()
Dim nameOfControl = "NameOfControl"
Dim child = visuals.OfType(Of FrameworkElement)().FirstOrDefault(Function(x) x.Name = nameOfControl)
child.Visiablity = Visibility.Collapsed
FrameworkElement can be replaced if you know what the type of the child control is. Note that if there are multiple children with the same name, only one of those children will be returned. Use Where() instead of FirstOrDefault() if you want to get them all.
Disclaimer: I am a C# programmer, all of this VB.Net code was converted from C# to VB using telerik's converter found here. There may be syntax or other errors in this code.