<Extension(), DebuggerHidden()>
Public Sub InvokeIfRequired(control As Control, action As MethodInvoker)
    If control.InvokeRequired Then control.Invoke(action) Else action()
End Sub
' No parameters
<Extension(), DebuggerHidden()>
Public Function InvokeIfRequired(Of TR)(control As Control, func As Func(Of TR)) As TR
    If control.InvokeRequired Then
        Return control.Invoke(func)
    Else
        Return func.Invoke()
    End If
End Function
' One parameter
<Extension(), DebuggerHidden()>
Public Function InvokeIfRequired(Of T1, TR)(control As Control, func As Func(Of T1, TR), arg1 As T1) As TR
    If control.InvokeRequired Then
        Return CType(control.Invoke(func, arg1), TR)
    Else
        Return func.Invoke(arg1)
    End If
End Function
' n parameters can be extrapolated...