[RESOLVED] VB.Net > ASP - What I thought should work, isn`t

Hi

I need a pointer in the right direction or I think I just wont bother messing with .net.... sigh

Code:

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                Response.Write("<p>jeito 1</p>")

                'assume that the order of the elements is generated properly
                'so that there is a 'tree' of elements to build
                Dim dOrder As New Stack
                Dim objOpenOrder(2000) As clsHtmlElement
                Dim aParents(2000) As String
                Dim lngWhichNivel As Long
                Dim lngOpenOrder As Long
                Dim lngOpenCtrl As Long
                Dim lngCtrl As Long
                Dim sRes As New StringBuilder

                lngOpenOrder = 0
                lngWhichNivel = 1
                cForm.setTheNivel(lngWhichNivel)
                objOpenOrder(lngOpenOrder) = cForm
                aParents(lngOpenOrder) = ""

                lngOpenOrder += 1
                lngWhichNivel = 2
                cDiv.setTheNivel(lngWhichNivel)
                cDiv.setParentHtmlId(cForm.getTheID())
                objOpenOrder(lngOpenOrder) = cDiv

                lngOpenOrder += 1
                lngWhichNivel = 3
                cLbl.setTheNivel(lngWhichNivel)
                cLbl.setParentHtmlId(cDiv.getTheID())
                objOpenOrder(lngOpenOrder) = cLbl

                lngOpenOrder += 1
                cDiv2.setParentHtmlId(cDiv.getTheID())
                cDiv2.setTheNivel(lngWhichNivel)
                objOpenOrder(lngOpenOrder) = cDiv2

                If lngOpenOrder > 0 Then
                        lngCtrl = 0
                        Response.Write(objOpenOrder(lngCtrl).htmlStart())
                        dOrder.Push(lngCtrl)

                        For lngCtrl = 1 To lngOpenOrder

                                If objOpenOrder(lngCtrl).getTheNivel() < objOpenOrder(dOrder.Peek()).getTheNivel() Then
                                        Do While objOpenOrder(lngCtrl).getTheNivel() < objOpenOrder(dOrder.Peek()).getTheNivel()
                                                lngOpenCtrl = dOrder.Pop()
                                                Response.Write(objOpenOrder(lngOpenCtrl).htmlEnd())
                                        Loop
                                Else

                                        If objOpenOrder(lngCtrl).getTheNivel() = objOpenOrder(dOrder.Peek()).getTheNivel() Then
                                                lngOpenCtrl = dOrder.Pop()
                                                Response.Write(objOpenOrder(lngOpenCtrl).htmlEnd())
                                        End If
                                End If

                                If lngCtrl <= lngOpenOrder Then
                                        Response.Write(objOpenOrder(lngCtrl).htmlStart())
                                        dOrder.Push(lngCtrl)
                                End If

                        Next

                End If

                'should be one open class minimum
                'any open classes...
                lngOpenCtrl = dOrder.Pop()
                Response.Write(objOpenOrder(lngOpenCtrl).htmlEnd())
                If (lngOpenCtrl > 0) Then
                        Do Until objOpenOrder(lngOpenCtrl).getTheNivel() <= 1
                                lngOpenCtrl = dOrder.Pop()
                                Response.Write(objOpenOrder(lngOpenCtrl).htmlEnd())
                        Loop
                End If

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This is a first attempt at using vb.net coming from an MS Access/VBA background with a little experience in VB6. Currently using Java/JSP at work.

I managed to create the base class and use new classes extending that.
But I am trying to hold objects of the classes in an array and I thought if I declared the array of the base class I could use any object based off of it. Apparently not as when running with a debug, and using the immediates window it is returning some weird stuff or using the methods of the base instead of the class. So I have obviously got it all wrong...

So.... what to do?

have you tried using a list of <T> (where <T> is your object)?

Can I use the base class as T though ?

yes in VB its

Code:

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dim x as List(of MyObj)

' to get things out
for each y as MyObj in x
y.firstproperty...
next

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I'll post the code later on, but I updated to use that list dropping in my base class.
Still didn't like it.
I think I'm missing something or perhaps I just need to use Object ?

Quote:

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Originally Posted by Ecniv

I'll post the code later on, but I updated to use that list dropping in my base class.
Still didn't like it.
I think I'm missing something or perhaps I just need to use Object ?

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You virtually never need to use Object, if you have a base class you are inheriting from have you marked the methods in the base class as Overridable and in the derived classes used the Overrides keyword?

Code:

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                Dim dOrder As New Stack
                Dim objOpenOrder As New List(Of clsHtmlElement)
                Dim aParents(2000) As String
                Dim lngWhichNivel As Long
                Dim lngOpenOrder As Long
                Dim lngOpenCtrl As Long
                Dim lngCtrl As Long
                Dim sRes As New StringBuilder

                lngOpenOrder = 0
                lngWhichNivel = 1
                cForm.setTheNivel(lngWhichNivel)
                objOpenOrder.Add(cForm)
                aParents(lngOpenOrder) = ""

                lngOpenOrder += 1
                lngWhichNivel = 2
                cDiv.setTheNivel(lngWhichNivel)
                cDiv.setParentHtmlId(cForm.getTheID())
                objOpenOrder.Add(cDiv)

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Ah hmm ... no and yes.

I use the overrides on the child class...

easier if I post the code for the classes...
Base Class :

Code:

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Imports Microsoft.VisualBasic

Public Class clsHtmlElement

        Private useVersion As Long
        Private lngNivel As Long
        Private strTheId As String = ""
        Private strTheName As String = ""
        Private strTheText As String = ""
        Private strTheLink As String = ""
        Private strTheTitle As String = ""
        Private strTheStyle As String = ""
        Private strClassName As String = ""
        Private strParentID As String = ""

        Public Sub New()
                useVersion = 1
        End Sub

        Public Function getTheNivel() As Long
                getTheNivel = lngNivel
        End Function

        Public Sub setTheNivel(l As Long)
                lngNivel = l
        End Sub

        Public Function getUseVersion() As Long
                Return useVersion
        End Function

        Public Sub setUseVersion(l As Long)
                useVersion = l
        End Sub

        Public Function getTheID() As String
                Return strTheId
        End Function

        Public Sub setTheID(s As String)
                strTheId = s
        End Sub

        Public Function getName() As String
                Return strTheName
        End Function

        Public Sub setName(s As String)
                strTheName = s
        End Sub

        Public Function getText() As String
                Return strTheText
        End Function

        Public Sub setText(s As String)
                strTheText = s
        End Sub

        Public Function getLink() As String
                Return strTheLink
        End Function

        Public Sub setLink(s As String)
                strTheLink = s
        End Sub

        Public Function getClassName() As String
                Return strClassName
        End Function

        Public Sub setClassName(s As String)
                strClassName = s
        End Sub

        Public Function getTheTitle() As String
                Return strTheTitle
        End Function

        Public Sub setTheTitle(s As String)
                strTheTitle = s
        End Sub

        Public Function getTheStyle() As String
                Return strTheStyle
        End Function

        Public Sub setTheStyle(s As String)
                strTheStyle = s
        End Sub

        Public Function htmlStart() As String
                Return ""
        End Function

        Public Function htmlEnd() As String
                Return ""
        End Function

        Public Function getParentHtmlId() As String
                Return strParentID
        End Function

        Public Sub setParentHtmlId(s As String)
                strParentID = s
        End Sub
End Class

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a child class

Code:

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Imports Microsoft.VisualBasic

Public Class clsLabel

        Inherits clsHtmlElement

        Private strForId As String

        Public Function getForId() As String
                Return strForId
        End Function

        Public Sub setForId(s As String)
                strForId = s
        End Sub


        Public Overloads Function htmlStart() As String
                Dim sRes As New StringBuilder

                sRes.Append("<label")
                If (getTheID().Length > 0) Then sRes.Append(" id=" + Chr(34) + getTheID() + Chr(34))
                If (getName().Length > 0) Then sRes.Append(" name=" + Chr(34) + getName() + Chr(34))
                If (getTheID().Length > 0) Then sRes.Append(" for=" + Chr(34) + strForId + Chr(34))
                sRes.AppendLine(">" + getText())

                Return sRes.ToString()
        End Function

        Public Overloads Function htmlEnd() As String
                Return "</label>"
        End Function

End Class

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Ah, you are Overloading not overriding, there is a big difference.

If you have methods in a base class that you want a derived class to be able to replace then the base class needs to mark them as overridable (similar to virtual in Java), the derived class then needs to mark it's implementation as overrides to get the polymorphic behaviour you want.

You've actually used Overloads rather than Overrides, and they are different.

Overloads allows you to create multiple routines with the same name, but using different parameter lists (so they can be used as a more efficient version of Optional parameters). This would be useful if you wanted to have variations of the routine at the same level, but it isn't what you want here.

Overrides is to allow you to replace the inherited routine, which is what you want here.

So, clsHtmlElement should have these changes:

Code:

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        Public Overridable Function htmlStart() As String
                Return ""
        End Function

        Public Overridable Function htmlEnd() As String
                Return ""
        End Function

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...and clsLabel should have these changes:

Code:

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        Public Overrides Function htmlStart() As String
...
        Public Overrides Function htmlEnd() As String

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edit: I should have refreshed the page, oops!

Thanks.
That makes sense. I'll have a go tonight and post back when it breaks .. or if it works :)

Hi

Thank you for the assist. I changed the overidable and overrides parts and once I`d updated all the classes, actually works :)

I`ll post up with more woes later on when I`ve got to the next problem :)

night all!

Quote:

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Originally Posted by Ecniv

Hi
I`ll post up with more woes later on when I`ve got to the next problem :)

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remember, if debugging is the science of taking the bugs out.

programming is the art of putting them in :D