Conversion from a base class

[Michael D. Ober]

I have a class:
Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On flags
this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[Tom Leylan]

I guess the standard question is "why?" You'll agree that a
StringCollection <ClientList, so what creates the "need?"
"Michael D. Ober" <obermd.@.alum.mit.edu.nospamwrote in message
news:u2**************@TK2MSFTNGP02.phx.gbl...

>I have a class:
Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On flags
this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[wfairl]

Create a constructor in the derived class that accepts an instance of
the base class.

On Jan 23, 2:21 pm, "Michael D. Ober" <obermd.@.alum.mit.edu.nospam>
wrote:

I have a class:

Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On flags
this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[_AnonCoward]

"Michael D. Ober" <obermd.@.alum.mit.edu.nospamwrote in message
news:u2**************@TK2MSFTNGP02.phx.gbl...
:
: I have a class:
:
:
: Private Class ClientList
: Inherits StringCollection
:
: Public InternalUser As Boolean = False
:
: Public Shadows Function Contains(ByVal ClientNumber As String) As
: Boolean
: If InternalUser Then Return True
: Return MyBase.Contains(ClientNumber)
: End Function
: End Class
:
: I need to do the following:
:
: dim mClientList as ClientList
: dim mStringCollection as new StringCollection
:
: mClientList = mStringCollection.
:
: What do I do to my class definition to allow this? Option Strict On
: flags this as an illegal implicit conversion. I'm open to using
: mClientList = new ClientList(mStringCollection) as well.
:
: Thanks,
: Mike Ober.
Use this syntax:

mClientList = CType(mStringCollection, ClientList)

That said, don't actually try this. What you are doing here doesn't
make sense. Your new derived class ClientList exposes a new bit of
functionality (the InternalUser field) not found in the base
StringCollection Class. If you assign an instance of a
StringCollection type to the mClientList variable, your code would end
up choking if it ever tried to access that property. The following
compiles fine, but throws an error when run:
Dim mClientList As ClientList
Dim mStringCollection As New StringCollection

mClientList = CType(mStringCollection, ClientList)

'oops: can't get to the InternalUser field!
Console.WriteLine(mClientList.InternalUser)

The CType() method gets rid of that pesky compiler error, but the code
still bombs when you get to the WriteLine statement because while the
mClientList type (ClientList) exposes the InternalUser property, the
instance you are referencing (StringCollection) does not.

Now, it does work in reverse:

mStringCollection = mClientList

This compiles and runs without issue because the ClientList type
inherits from the StringCollection type and therefore exposes all of
the functionality of that base type (the functionality may be
overridden, but it's there). You'll never be able to access the
InternalUser property as long as the code think's it's working with an
instance of the StringCollection type, but that isn't an issue - there
are ways around that. For example, you can do the following:
Dim mClientList As New ClientList
Dim mStringCollection As StringCollection

mStringCollection = mClientList

Dim intUser As Boolean
intUser = CType(mStringCollection, ClientList).InternalUser

Console.WriteLine(intUser)
Ralf
--
--
----------------------------------------------------------
* ^~^ ^~^ *
* _ {~ ~} {~ ~} _ *
* /_``>*< >*<''_\ *
* (\--_)++) (++(_--/) *
----------------------------------------------------------
There are no advanced students in Aikido - there are only
competent beginners. There are no advanced techniques -
only the correct application of basic principles.

[Michael D. Ober]

OK - I tried and came up blank before I posted my original message. How do
I assign the base class object?

public sub New(ByVal sc as StringCollection)
' What goes here? I can't use "mybase = sc"
' Do I actually need to loop through sc and add each element to mybase
mybase.new()
for each s as String in sc
mybase.Add(s)
next s
end sub

Thanks,
Mike.
<wf****@gmail.comwrote in message
news:11**********************@13g2000cwe.googlegro ups.com...

Create a constructor in the derived class that accepts an instance of
the base class.

On Jan 23, 2:21 pm, "Michael D. Ober" <obermd.@.alum.mit.edu.nospam>
wrote:

>I have a class:

Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On
flags
this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[Michael D. Ober]

Business Rules create the need.

Mike.

"Tom Leylan" <tl*****@nospam.netwrote in message
news:eK**************@TK2MSFTNGP06.phx.gbl...

>I guess the standard question is "why?" You'll agree that a
StringCollection <ClientList, so what creates the "need?"
"Michael D. Ober" <obermd.@.alum.mit.edu.nospamwrote in message
news:u2**************@TK2MSFTNGP02.phx.gbl...

>>I have a class:
Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On
flags this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[Tom Leylan]

I suppose I was a bit too cryptic. A StringCollection isn't a ClientList so
unless something changes in the way OOP is implemented in DotNet I don't
think you'll just pass a reference and have it magically connect up.

You can copy the elements in the StringCollection into the ClientList and
probably fairly quickly using CopyTo and AddRange(). I could be mistaken
but I don't think you'll find syntax that will permit what you are hoping to
do.

Tom
"Michael D. Ober" <obermd.@.alum.mit.edu.no.spamwrote in message
news:za******************@newsread1.news.pas.earth link.net...

Business Rules create the need.

Mike.

"Tom Leylan" <tl*****@nospam.netwrote in message
news:eK**************@TK2MSFTNGP06.phx.gbl...

>>I guess the standard question is "why?" You'll agree that a
StringCollection <ClientList, so what creates the "need?"
"Michael D. Ober" <obermd.@.alum.mit.edu.nospamwrote in message
news:u2**************@TK2MSFTNGP02.phx.gbl...

>>>I have a class:
Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On
flags this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[Cor Ligthert [MVP]]

Business Rules create the need.

>
Mike.

Mike,

I cannot resist on this, this kind of answers let me think about

Is there to a Business Rule that say thay you have to pee with your head in
the urinal and everybody is doing their best to fullfil that.

Cor

[Michael D. Ober]

It turns out that the only place where I need to convert the
StringCollection to ClientList is in a line such as:

dim sc as StringCollection
dim cl as ClientList
' do some processing that may or may not create an actual StringCollection
if sc is Nothing then cl = new ClientList else cl = new ClientList(sc)

The code in this application is littered with cl.Contains, which as I stated
in another clarification post, sometimes needs to always return true (this
is actually part of a web-site and internal users get additional features)

I ended up implementing ClientList.New(StringCollection) by interating
through the collection and adding it to mybase.items.

Thanks for all the feedback.
Mike Ober.

"Tom Leylan" <tl*****@nospam.netwrote in message
news:ua**************@TK2MSFTNGP06.phx.gbl...

>I suppose I was a bit too cryptic. A StringCollection isn't a ClientList
so unless something changes in the way OOP is implemented in DotNet I don't
think you'll just pass a reference and have it magically connect up.

You can copy the elements in the StringCollection into the ClientList and
probably fairly quickly using CopyTo and AddRange(). I could be mistaken
but I don't think you'll find syntax that will permit what you are hoping
to do.

Tom
"Michael D. Ober" <obermd.@.alum.mit.edu.no.spamwrote in message
news:za******************@newsread1.news.pas.earth link.net...

>Business Rules create the need.

Mike.

"Tom Leylan" <tl*****@nospam.netwrote in message
news:eK**************@TK2MSFTNGP06.phx.gbl...

>>>I guess the standard question is "why?" You'll agree that a
StringCollection <ClientList, so what creates the "need?"
"Michael D. Ober" <obermd.@.alum.mit.edu.nospamwrote in message
news:u2**************@TK2MSFTNGP02.phx.gbl...
I have a class:
Private Class ClientList
Inherits StringCollection

Public InternalUser As Boolean = False

Public Shadows Function Contains(ByVal ClientNumber As String) As
Boolean
If InternalUser Then Return True
Return MyBase.Contains(ClientNumber)
End Function
End Class

I need to do the following:

dim mClientList as ClientList
dim mStringCollection as new StringCollection

mClientList = mStringCollection.

What do I do to my class definition to allow this? Option Strict On
flags this as an illegal implicit conversion. I'm open to using

mClientList = new ClientList(mStringCollection) as well.

Thanks,
Mike Ober.

[Tom Leylan]

"Cor Ligthert [MVP]" <no************@planet.nlwrote in message
news:OI**************@TK2MSFTNGP02.phx.gbl...

Is there to a Business Rule that say thay you have to pee with your head
in the urinal and everybody is doing their best to fullfil that.

I'd just like to save everybody the effort and point out that I have indeed
tried this and while it may seem practical at first, it does not work!

[Ravichandran J.V.]

You would need to overload the = operator with the implicit / explicit
keyword. The operator overloading method should return a type of the
other class.

with regards,
J.V.Ravichandran
- http://www.geocities.com/
jvravichandran
- Or, just search on "J.V.Ravichandran"
at http://www.Google.com

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