Class, property and list
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Thread: Class, property and list

  1. #1
    Join Date
    Sep 2012
    Posts
    12

    Class, property and list

    Here some code about something i seem not to get working...
    1) first part is a class and it works
    2) button1 works
    3) why doenst allow me to retrieve the value of the list i made like bakjeList.count?

    It says BakjeList is not declared.. etc, but how to declare it right?


    Code:
    Public Class Class_BaanAsBakje
        REM ************************************************
        REM * Fields voor de bakjes van de baan
        REM ************************************************
        Private mXlineBakje As Single
        Private mYlineBakje As Single
        Private mWaarde As Single
    
    
        REM ************************************************
        REM * Properties voor de bakjes van de baan
        REM ************************************************
        Public Property XlineBakje As Single
            Get
                Return mXlineBakje
    
            End Get
            Set(ByVal value As Single)
                mXlineBakje = value
    
            End Set
        End Property
    
        Public Property YlineBakje As Single
            Get
                Return mYlineBakje
    
            End Get
            Set(ByVal value As Single)
                mYlineBakje = value
            End Set
        End Property
        Public Property Waarde As Single
            Get
                Return mWaarde
            End Get
            Set(ByVal value As Single)
                mWaarde = value
            End Set
        End Property
    
        Public Sub New(ByVal xlineBakje As Single, ByVal ylinebakje As Single, ByVal waarde As Single)
    
            mXlineBakje = xlineBakje
            mYlineBakje = ylinebakje
            mWaarde = waarde
        End Sub
    
    End Class
    Code:
    Public Class Form1
    
        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            Dim bakjesList As New List(Of Class_BaanAsBakje)
            bakjesList.Clear()
            ListBox1.Items.Clear()
            For i = 0 To 100
                Dim bakje As Class_BaanAsBakje = New Class_BaanAsBakje(i, i + 1, i + 3)
                bakjesList.Add(bakje)
                ListBox1.Items.Add(bakje.XlineBakje & " " & bakje.YlineBakje & " " & bakje.Waarde)
            Next
            Dim test As Integer
            test = bakjesList.Count()
            bakjesList.RemoveAt(5)
    
            For i = 0 To bakjesList.Count - 1
                ListBox1.Items.Add(bakjesList(i).XlineBakje & " " & bakjesList(i).YlineBakje & " " & bakjesList(i).Waarde)
            Next
    
        End Sub
    
        Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    
            ' Dim bakjesList As List(Of Class_BaanAsBakje)
            Dim test2 As Integer
            test2 = bakjesList.Count()
    
        End Sub
    End Class

  2. #2
    Join Date
    Sep 2000
    Location
    FL
    Posts
    1,451

    Re: Class, property and list

    Your issue has to do with the scope of your object. When you declare an object inside a function, it will only exist for that function. Declare it for the class, and it will exist for the whole class. I would suggest something like....

    Code:
    Public Class Form1
        Private bakjesList As New List(Of Class_BaanAsBakje)
    
        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            bakjesList.Clear()
            ListBox1.Items.Clear()
            For i = 0 To 100
                Dim bakje As Class_BaanAsBakje = New Class_BaanAsBakje(i, i + 1, i + 3)
                bakjesList.Add(bakje)
                ListBox1.Items.Add(bakje.XlineBakje & " " & bakje.YlineBakje & " " & bakje.Waarde)
            Next
            Dim test As Integer
            test = bakjesList.Count()
            bakjesList.RemoveAt(5)
    
            For i = 0 To bakjesList.Count - 1
                ListBox1.Items.Add(bakjesList(i).XlineBakje & " " & bakjesList(i).YlineBakje & " " & bakjesList(i).Waarde)
            Next
    
        End Sub
    
        Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    
            Dim test2 As Integer
            test2 = bakjesList.Count()
    
        End Sub
    End Class

  3. #3
    Join Date
    Sep 2012
    Posts
    12

    Re: Class, property and list

    True that was the solution as slowly i start to understand that public is not as public as in VB6......

    Thanx for showing your experience, as its clearly a noob error, but as stated before it feels so different to vb6, the learning curve is much different as well....

    But I keep continuing.....

  4. #4
    Join Date
    Sep 2000
    Location
    FL
    Posts
    1,451

    Re: Class, property and list

    It is different, but you will find that it is also easier in many ways, and also in many ways more powerful.

    Keep plugging away and come back here when you need help

  5. #5
    DataMiser is offline Super Moderator Power Poster
    Join Date
    Jul 2008
    Location
    WV
    Posts
    4,830

    Re: Class, property and list

    Quote Originally Posted by Joska Paszli View Post
    True that was the solution as slowly i start to understand that public is not as public as in VB6......

    Thanx for showing your experience, as its clearly a noob error, but as stated before it feels so different to vb6, the learning curve is much different as well....

    But I keep continuing.....
    Actually if you dim a variable inside a function using VB6 you will get an error if you try to reference that variable in a different function. The variable is only known to the function where it is defined and must be defined outside the functions to be visible to the entire form, module or class and must be Public to be seen outside the form, module or class this is the same in VB6 and VB.Net. While there are some differences they are very much the same as well.
    Always use [code][/code] tags when posting code.

  6. #6
    Join Date
    Jul 2001
    Location
    Sunny South Africa
    Posts
    11,091

    Re: Class, property and list

    This is issue is at the very heart of OOP. You must understand scope properly in order to use it properly. I'd suggest you get a book on that, or google it :

    https://www.google.co.za/search?q=oo...ient=firefox-a

  7. #7
    Join Date
    Sep 2012
    Posts
    12

    Re: Class, property and list

    true i have 2 books now but still i find it is not getting enough weight in books or examples.... also te most common examples are for such a small, simple example (ofcourse) but a step by step explanation what u can do with it in combination with each other could get more attention.... also the flexibility and power makes it hard but now after 2 weeks/100 hours i see more and more light... a steep learning curve.... i cant say i miss vb6 but i still miss the speed in which i can programm.... it really takes much time

  8. #8
    DataMiser is offline Super Moderator Power Poster
    Join Date
    Jul 2008
    Location
    WV
    Posts
    4,830

    Re: Class, property and list

    Once you have a handle on the VB.Net classes and usage you may find that you can write programs faster in VB.Net and that you can with a little planning reuse a lot of your code.

    I think the thing that stumped me the most was the transition from ADO Connections and Recordsets to ADO.Net datasets, datatables and datareaders.
    Always use [code][/code] tags when posting code.

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