Object-Oriented Programming

[Aeric]

I am currently learning to use ASP.NET 2.0 with Visual Web Developer.
For my previous project, I used ASP 3.0 with OOP approach where all my files are .asp regardless they are ASP page or class file.
In .NET, we can use code behind and Master/Detail design.
I tried to practice OOP approach in ASP.NET but yet find any sample or tutorial for it.
I tried to use a class file (eg. Bank.vb) where it will stored inside App_Code folder.

Bank.vb:

Public Class Bank
    Private strProperty1 As String
    Private strProperty2 As String

    Public Property Property1() As String
        Get
            Return strProperty1
        End Get
        Set(ByVal value As String)
            strProperty1 = value
        End Set
    End Property

    Public Property Property2() As String
        Get
            Return strProperty2
        End Get
        Set(ByVal value As String)
            strProperty2 = value
        End Set
    End Property
End Class

In MasterPage.master.vb, I have:

Partial Class MasterPage
    Inherits System.Web.UI.MasterPage

    Private objBank As New Bank

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Page.IsPostBack Then
            objBank.Property1 = DropDown1.SelectedValue
            objBank.Property2 = DropDown2.SelectedValue
        End If
    End Sub

    Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
        If RadioButton1.SelectedIndex = 1 Then
            Response.Redirect("BankReport.aspx")
        Else
            Response.Redirect("ProductReport.aspx")
        End If
    End Sub

    Protected Overrides Sub Finalize()
        objBank = Nothing '<-Required?
        MyBase.Finalize()
    End Sub
End Class

ProductReport.aspx.vb:

Imports Bank

Partial Class ProductReport
    Inherits System.Web.UI.Page

    Public oBank As New Bank

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Response.Write(oBank.Property1) '<- oBank.Property1 = Nothing
    End Sub

    Protected Overrides Sub Finalize()
        oBank = Nothing '<-Required?
        MyBase.Finalize()
    End Sub
End Class

My problem is why oBank.Property1 = Nothing ?
It should has a value from DropDown1.SelectedValue when I click btnSubmit.
For example, DropDown1.SelectedValue = "Public Bank LLC"
Then this value will assign to Property1 through objBank.Property1
and share in ProductReport.aspx using oBank.Property1
Can you tell me what's wrong with my code?

Should I initialize all my variables in Bank.vb class using:

    Public Sub New()
        strProperty1 = ""
        strProperty2 = ""
    End Sub

Finally, do I need to dereference the objBank and oBank using Finalize Sub?

[mendhak]

MasterPage.master.vb is a class file. ProductReport.aspx.vb is another class file. They are not the same class file. Therefore when you instantiate Bank on ProductReport, it won't have any property values unless you give it property values.

Remember that a MasterPage is not a base class to any child page. It's just a master page in terms of the page layout and markup.

If you want to access the properties of the Bank object from a page that uses a MasterPage, you will first need to make the Bank object available as a property of the MasterPage. Then in your 'child' page, take Me.Page.Master, convert it to the type of your master page (in other words, the class name of your Master Page which just happens to be MasterPage) and that property is then available for you to use.

[Aeric]

Then in your 'child' page, take Me.Page.Master, convert it to the type of your master page...

I am not very clear with this statement. How to convert?

[mendhak]

Using CType. Like this

Dim myMasterPage as MasterPage = CType(Me.Page.Master, MasterPage)
TextBox1.Text = myMasterPage.MyPropertyName

[Aeric]

I will try and see. Thanks.

[Aeric]

I can use Function and Subroutine from the class but the values of class property are reinitialized every time the page.aspx loaded.
Is there any way to keep the values instead of using Session?

[mendhak]

You can use Session or Viewstate. Viewstate helps persist data across postbacks but it's never a good idea to put too much data or secure data in viewstate because viewstate actually goes back to the client on each postback.

[Aeric]

Thanks for introducing to me on Viewstate.
Does this mean that using Class is not the solution to keep the values?

I am working on reporting so I will need to pass the common parameters like Year, Month and some Level Codes through out the drill-down reports.

[mendhak]

No no, I didn't mean to say that.

What I mean is if you have a lot of data and/or sensitive data, then you shouldn't use viewstate.

In your case, you seem to have a class that contains just a few properties. Year, Month, Level Codes. Assuming 'level codes' aren't a sensitive piece of information, this means that the XML for the viewstate (when you put something in viewstate, it is serialized) won't be that big, so you should be alright with it.

The same thing happens with the session variable - it gets serialized - but the client is sent a 'sessionid' cookie which helps match the right session variable with the right person. The advantage of the session variable is that the user can't see what the session variable actually contains.