referencing form button from another form - vb.net

Question

I have two forms both with the same buttons on, and I want to have it so that if I click the button both buttons will do the same thing i.e. they are referencing each other on different forms. the way i found was:
Public Class Form2
Dim form1 As New form1
Private Sub Button2_Click
form1.backcolor=black
form2.backcolor=black
end sub
end class
then
Public Class Form1
Dim form2 As New form2
Private Sub Button1_Click
form1.backcolor=black
form2.backcolor=black
end sub
end class
only this doesn't work as there is an error:An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll as far as i can see there is no infinite loop or stack over flow.
any help would be greatly appreciated.

Answer 1

You have an infinite loop, because each time one of the forms is instantiated, it is instantiating the other. Creating a Form1 will create a Form2, then Form2 immediately creates another Form1 and so on and so on...
Change your code to this:
Public Class Form2
Private Sub Button2_Click
Dim form1 As New Form1
form1.backcolor=black
form2.backcolor=black
End sub
End class
Public Class Form1
Private Sub Button1_Click
form1.backcolor=black
Dim form2 As New Form2
form2.backcolor=black
End sub
End class
Now it will only create the other class instances when you click a button.

Answer 2

Like Karl Anderson said, there is a infinite loop in your code. His solution will create a new form every time you click the button. If you don't want this behavior, I think that the best approach is to use the mediator pattern. And it will be much more easy if you want to add new actions and new forms.
The code will look something like this:
Public Class Mediator
Private forms As New List(Of BaseForm)
Public Sub RegisterForm(form As BaseForm)
forms.Add(form)
End Sub
Public Sub ChangeAllFormsBackColorToBlack()
For Each form In forms
form.ChangeBackColorToBlack()
Next
End Sub
End Class
Public Class BaseForm
Private med As Mediator
Public Sub New(med As Mediator)
Me.med = med
Me.med.RegisterForm(Me)
End Sub
Public Sub ChangeBackColorToBlack()
backcolor = black
End Sub
Public Sub OnButtonClick()
Me.med.ChangeAllFormsBackColorToBlack()
End Sub
End Class
Public Class Form2
Inherits BaseForm
Public Sub New(med As Mediator)
MyBase.New(med)
End Sub
Private Sub Button2_Click()
Me.OnButtonClick()
End Sub
End Class
Public Class Form1
Inherits BaseForm
Public Sub New(med As Mediator)
MyBase.New(med)
End Sub
Private Sub Button1_Click()
Me.OnButtonClick()
End Sub
End Class
Module MediatorDemo
Sub Main()
Dim med As New Mediator
Dim f1 As New Form1(med)
Dim f2 As New Form2(med)
f1.OnButtonClick()
End Sub
End Module