How to retain the 'New' constructor across subclasses? - vb.net

Question

Let's start with an example Module:
Module PuppyKillers
Public Puppies As Double = 135
Public SquadSize As Integer = 5
Class PuppyKiller
Private KillingTimer As New System.Timers.Timer _
With {.AutoReset = True, .Interval = 1000, .Enabled = False}
Public PuppiesPerSecond As Double = 0.5
Public name As String = "John Doe"
Public Sub New(Optional param As Double = 1)
PuppiesPerSecond = PuppiesPerSecond * param
AddHandler KillingTimer.Elapsed, AddressOf KillPuppies
End Sub
Private Sub KillPuppies(ByVal sender As Object, _
ByVal e As System.Timers.ElapsedEventArgs)
If Puppies <= 0 Then
Me.Killing = False
Else
Puppies -= PuppiesPerSecond
End If
End Sub
Property Killing As Boolean
Get
Return KillingTimer.Enabled
End Get
Set(value As Boolean)
KillingTimer.Enabled = value
End Set
End Property
End Class
Class ChiefPuppyKiller
Inherits PuppyKiller
End Class
Sub Exterminators_Start() ' 4 Killers + 1 Chief
Dim squad As New ArrayList
REM The following line prevents the compilation.
squad.Add(New ChiefPuppyKiller(3)) 'A chief kills 3 times the normal amount.
For i As Integer = 1 To SquadSize - 1
squad.Add(New PuppyKiller)
Next
REM Start the slaughter
Console.WriteLine("Puppies: " & Puppies)
For Each c As PuppyKiller In squad
c.Killing = True
Next
Do
Threading.Thread.Sleep(4737)
Console.WriteLine("Remaining Puppies: " & Math.Ceiling(Puppies))
Application.DoEvents()
If Puppies = 0 Then
Console.WriteLine("Meow: No more puppies.")
Exit Do
End If
Loop
End Sub
End Module
I've a problem with the above block of code: I cannot find a way to use PuppyKiller's Constructor from its subclasses: ChiefPuppyKiller in this case.
I got an error about the number of parameters for the constructor, so I assume that the base class constructor is not used.
I don't want to declare a new New sub for every subclass. But I'd like to be able to specify the puppy killing multiplier in the constructor.
Note: no animal has been harmed while writing this question, as the code does not compile.

Answer 1

You are going to have to add a new constructor for every class where you want to pass that value in:
Class ChiefPuppyKiller
Inherits PuppyKiller
Public Sub New(param As Double)
MyBase.New(param)
End Sub
End Class