Visual Basic

Friend Function LineCheck(ByVal LineIn As Line) As Line()
   Dim LineOut() As Line
   If LineIn.Field1 = "" Then AddError(LineIn, "Field1 Blank", LineOut)
   If LineIn.Field2 = "" Then AddError(LineIn, "Field2 Blank", LineOut)
   If LineIn.Field3 = "" Then AddError(LineIn, "Field3 Blank", LineOut)
   If LineIn.Field4 = "" Then AddError(LineIn, "Field4 Blank", LineOut)
   Return LineOut
End Function

Friend Sub AddError(ByVal LineIn As Line, ByVal LineError As String, ByRef LineOut() As Line)
   Dim tmp As New Line
   tmp = LineIn
   tmp.LineError = LineError
   If Not LineOut Is Nothing Then ReDim Preserve LineOut(LineOut.Length) Else ReDim Preserve LineOut(0)
   LineOut(LineOut.Length - 1) = New Line
   LineOut(LineOut.Length - 1) = tmp
End Sub

public class form1
   inherits system.windows.forms.form

'initialization code

private m_productCode as String

friend property ProductCode() as String
   Get
      return me.m_productCode
   End Get
   Set(byval value as string)
      me.m_productcode = value
   End Set
end property

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

   me.ProductCode = textbox1.text.substring(0, 4)

   dim frmTwo as new form2
   frmTwo.FormOne = me
   frmTwo.Show

end sub

end class

*'--- in a separate code file ---'*

class form2
   Inherits System.Windows.Forms.Form

private m_formOne as Windows.Forms.Form

Friend Property Form1 as Windows.Forms.Form
   Get
      return me.m_formOne
   End Get
   Set(byval value as Windows.Forms.Form)
      me.m_formOne = value
   End Set
End Property

Private Sub form2_Load(byval sender as object, byval e as system.eventargs) handles form2.Load

'--- this line gives you access to the product code from form1 ---'
dim productCode as string = me.FormOne.ProductCode

End Sub

end class