vb.net Why caint i write data to one class, but i can to another class?

Question

I have 3 classes,
class one - "card". this class contains properties
class two - "cardcollection". this class inherits list of the type card
class three-"flash". this class inherits list of the type card

This code works.

For i As Integer = 0 To _cardcollec.Count - 1
Dim _card As Card
_card = _cardcollec.Item(i)
_cardcollec.Add(_card)
Next

with this code, i get this error?
Object reference not set to an instance of an object.

For i As Integer = 0 To _cardcollec.Count - 1
Dim _card As Card
_card = _cardcollec.Item(i)
_flash.Add(_card)
Next

I dont understand
thanks
mike

here is where it crashes

_flash.Add(_card)

If i hover over _card, it contains the correct information.

Answer 1

Can't determine without seeing the code for Card and Flash, since Flash inherits from Card and the logic error could be in either.

Answer 2

the object _flash is not set to an instance of an object.
Before adding items to _flash you should instantiate it i.e. create a new instance of it

Dim _flash as New flash

Note: It does not make sense that CardCollection inherits Card. if it is a collection of Cards, it should inherit System.Collections.CollectionBase instead

Thank You.

Answer 3

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Answer 4

I would say you have not instantiated _flash e.g Not defined it so it is accessable in this scope.

I assume you have somewhere (globally ?)
Dim _cardcollec As Cardcollection
You have
Dim _card As Card in this routine.
Where is
Dim _flash As Flash ?