Using Color As Optional Parameter In a function within a class

Question

How can I declare an optional color parameter in some function or sub, as if I do that in the normal way (I mean to give some default color for that optional parameter) as t

Answer 1

In Visual Basic, the solution proposed by @Steve nearly works but setting Color to Nothing does not do what you might normally expect; the check needs to be for the Empty Color, not for Nothing. Here is an example. It Flashes a Windows Forms Control's BackColor for 50 milliseconds, so long as it has a .ForeColor:

Sub Flash(c As Control, Optional FlashColor As Color = Nothing,
          Optional Duration As Integer = 50)
    If FlashColor.Equals(System.Drawing.Color.Empty) Then FlashColor = Color.Red
    Try
        Dim CurrColor = c.BackColor
        c.BackColor = FlashColor
        c.Refresh()
        System.Threading.Thread.Sleep(Duration)
        c.BackColor = CurrColor
        c.Refresh()
    Catch ex as Exception
    End Try
End Sub