Collection

I have a class (called ConnectionCollection) that implements IList and ICollection
And i have also another class called ConnectionManager.

Only the ConnectionManager is allowed to Add, Insert and Remove objects to the ConnectionCollection. Other classes may only view the objects with the Item property (or by using an enumerator).
How can i make this possible?

You can't expose the ConnectionCollection outside the ConnectionManager class if that's the case. Usually you would have a setup like this:

VB Code:

Public Class ConnectionManager
    Private _connections As ConnectionCollection
 
    Public ReadOnly Property Connections() As ConnectionCollection
        Get
            If Me._connections Is Nothing Then
                Me._connections = New ConnectionManager
            End If
 
            Return Me._connections
        End Get
    End Property
 
End Class

You will not be able to do that though because then the caller would be able to call the methods of the ConnectionCollection object. Instead you must completely conceal the collection, which you can do like this:

VB Code:

Public Class ConnectionManager
    Private _connections As ConnectionCollection
 
    Public ReadOnly Property Connections(ByVal index As Integer) As Connection
        Get
            If Me._connections Is Nothing Then
                Me._connections = New ConnectionManager
            End If
 
            Return Me._connections(index)
        End Get
    End Property
 
End Class

Now all the caller can do is get a reference to a specific Connection object from the collection by providing an index. The property is ReadOnly so they cannot assign a new object to that index and they have no access to the collection itself.