How to add an optional parameters/default value parameters in VB function?

Use the Optional keyword and supply a default value. Optional parameters must be the last parameters defined, to avoid creating ambiguous function signatures.

Sub MyMethod(ByVal Param1 As String, Optional ByVal FlagArgument As Boolean = True)
    If FlagArgument Then
        'Do something special
        Console.WriteLine(Param1)
    End If

End Sub

Call it like this:

MyMethod("test1")

Or like this:

MyMethod("test2", False)