Question

I don’t know really how to word the question so please bear with me…

I have 3 classes: Server, Database, and Table. Each class has a “Name” property. How I want it to work is that each server can have multiple databases and each database can have multiple tables. So in the Server class I have this property.

Private _databases As List(Of Database)
Public Property Databases() As List(Of Database)
    Get
        Return _databases
    End Get
    Set(ByVal value As List(Of Database))
        _databases = value
    End Set
End Property

And I have something similar in the Database class for the tables. This works fine now because I can do something like this to get all the databases in the server.

For Each db In s.Databases 's being the server object
        Debug.Print(db.Name)

    Next

I would like to expand these classes. I want the server class to handle all the connection information and I would like the other classes to use the server class’s connection information in them.

For example, I setup a server class and set the connection string to the server. Then I want the database class to use serverclass.connectionstring property to connect to the server and get a list of all the databases. But I want to keep that code in the database class. How can I do this?

I’ve attached some code of what I want to do.

Public Class Server

Private _name As String
Public Property Name() As String
    Get
        Return _name
    End Get
    Set(ByVal value As String)
        _name = value
    End Set
End Property


Private _databases As List(Of Database)
Public Property Databases() As List(Of Database)
    Get
        Return _databases
    End Get
    Set(ByVal value As List(Of Database))
        _databases = value
    End Set
End Property
End Class

'-----New class  

Public Class Database

Private _name As String
Public Property Name() As String
    Get
        Return _name
    End Get
    Set(ByVal value As String)
        _name = value
    End Set
End Property


Private _tables As List(Of Table)
Public Property Tables() As List(Of Table)
    Get
        Return _tables
    End Get
    Set(ByVal value As List(Of Table))
        _tables = value
    End Set
End Property

'This is where I need help!
Private Sub LoadTables () 
    dim connectionstring as string = server.connectionstring 'Possible?

    'Do database stuff
End Class

Thanks for reading!

Answer 1

You’ll have to include a reference to the “owner” class in your child class.

Without using code (for the sake of brevity), you have right now

Server
----------
Databases   -----> Database
Name               ------------
                   Tables       -----> Table
                   Name                --------------
                                       Name

What you want is something like this:

Server
----------
Databases   -----> Database
Name               ------------
  ^                Tables       -----> Table
  |                Name                --------------
   --------------- Server              Name
                     ^                 Database
                     |-------------------|

The Server property on the Database class and the Database property on the Table class are intended to be references to the instance of each that owns them.