Declaration referenced in a method implementation can not be a final method.

[Bob]

I've been testing my business objects with a little driver program called
PSSDriver. It's a Windows Form project and I've been putting my code in the
Form Load.

The code is as follows:

Option Compare Text
Option Strict On

Imports PersonShowStationMaint ' The business objects DLL

Public Class Form1
Inherits System.Windows.Forms.Form

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load

Const MarkConn As String = "Integrated Security=SSPI;Persist Security
Info=False;Initial Catalog=Mark;Data Source=RAINSLEY"

Dim Show As New Show(MarkConn)
With Show
.GetById(90709)
.GetShowPeople()
End With

End Sub
End Class

The .GetById invocation works just fine and the Show object contains the
expected data. However, when I attempt to invoke the .GetShowPeople method, I
get the following error:

An unhandled exception of type 'System.TypeLoadException' occurred in
PSSDriver.exe

Additional information: Declaration referenced in a method implementation can
not be a final method. Type: PersonShowStationMaint.ShowPeople. Assembly:
Clear.

The declaration of the .GetById method is:

Public Function GetById(ByVal Id As Int32) As Boolean

and the declaration of the .GetShowPeople method is:

Public Sub GetShowPeople()

What am I doing wrong?

Thanks,

Bob

[Bob]

I'm making some progress. I was confused because the .GetShowPeople doesn't
have a .Clear method.

By process of elimination, I narrowed down the problem line in the method to
be:

mShowPeople.Add(ShowPerson)

mShowPeople is defined as:

Private mShowPeople As ShowPeople

ShowPeople is a typesafe collection class that does have a .Clear method. It
is defined as:

Option Compare Text
Option Strict On

Public Class ShowPeople

Inherits System.Collections.CollectionBase
Private mIdHashTable As New Hashtable()

Public Sub Add(ByVal ShowPerson As ShowPerson)
Me.List.Add(ShowPerson)
mIdHashTable.Add(CType(ShowPerson.Id, String), ShowPerson)
End Sub

Public Overrides Sub Clear()
MyBase.Clear()
mIdHashTable.Clear()
End Sub

Public ReadOnly Property IdHashTable() As Hashtable
Get
Return mIdHashTable
End Get
End Property

Default Property Item(ByVal Index As Int32) As ShowPerson
Get
Return CType(Me.List.Item(Index), ShowPerson)
End Get
Set(ByVal Value As ShowPerson)
Me.List.Item(Index) = Value
End Set
End Property

Default ReadOnly Property Item(ByVal Id As String) As ShowPerson
Get
Return CType(IdHashTable.Item(Id), ShowPerson)
End Get
End Property

Public Sub Remove(ByVal ShowPerson As ShowPerson)
Me.List.Remove(ShowPerson)
mIdHashTable.Remove(CType(ShowPerson.Id, String))
End Sub

Public Overrides Sub RemoveAt(ByVal Index As Int32)
Remove(Item(Index))
End Sub

End Class

What is the problem with how I've implemented Clear?

Thanks,

Bob

[Anthony Jones]

Bob,

I'm no expert but the docs for CollectionBase.Clear specifies that the Clear
sub is NotOverridable. Would that have anything to do with it?

--
Anthony Jones
Nuesoft Ltd

[Bob]

In article <3ce79e94@10.1.10.29>, anthony.jones@nonuesoft.spamco.uk says...
> Bob,
>
> I'm no expert but the docs for CollectionBase.Clear specifies that the Clear
> sub is NotOverridable. Would that have anything to do with it?
>
> --
> Anthony Jones
> Nuesoft Ltd
>
>
>
If that's the case, it would explain a lot. I do wonder why the compiler
didn't catch that though. It also means I need to go back and check the book
where I got the code.

Thanks, I go check that out.

Bob

[Bob]

In article <MPG.1752ae7b4e9c047d9896ea@news.devx.com>, no@spam.com says...
> In article <3ce79e94@10.1.10.29>, anthony.jones@nonuesoft.spamco.uk says...
> > Bob,
> >
> > I'm no expert but the docs for CollectionBase.Clear specifies that the Clear
> > sub is NotOverridable. Would that have anything to do with it?
> >
> > --
> > Anthony Jones
> > Nuesoft Ltd
> >
> >
> >
> If that's the case, it would explain a lot. I do wonder why the compiler
> didn't catch that though. It also means I need to go back and check the book
> where I got the code.
>
> Thanks, I go check that out.
>
> Bob
>
Anthony,

You were right. Checking out the errata for the book, it indicates that
Overrides should be changed to Shadows.

One would think that a book that purports to be for V1.0 would have gotten
this one right.

Bob

[Brad]

Bob, use Public Shadows instead of Public Overrides. This will fix your problem.

Brad

Bob <no@spam.com> wrote:
>In article <3ce79e94@10.1.10.29>, anthony.jones@nonuesoft.spamco.uk says...
>> Bob,
>>
>> I'm no expert but the docs for CollectionBase.Clear specifies that the
Clear
>> sub is NotOverridable. Would that have anything to do with it?
>>
>> --
>> Anthony Jones
>> Nuesoft Ltd
>>
>>
>>