Question

I having a problem in my website where I have 2 objects held in session, both object are structured differently and do not have any links to each other (not intentionally). Both objects however, have a collection of “Travellers”. What I am trying to do is modify one collection by adding or removing “Travellers”, when a finish button is clicked, the modified collection will then be saved to the other object.

The problem is that for some reason when I modify one collection in one object, the modifications are also made to the collection in the other object.

Here’s a rough example:

Dim bookingContext As BookingContext = Session("BookingContext")
Dim personSearchContext As PersonSearchContext = Session("PersonSearchContext")
Dim personId As Integer = Request.Form("PersonID")
Dim mode As String = Request.Form("Mode")

Select Case mode
    Case "Add"
        For Each traveller As PersonProfile In personSearchContext.Travellers
            If traveller.PersonID = personId Then
                personSearchContext.SelectedTravellers.Add(traveller)
                Exit For
            End If
        Next
        context.Session("PersonSearchContext") = personSearchContext
    Case "Remove"
        For Each traveller As PersonProfile In personSearchContext.SelectedTravellers
            If traveller.PersonID = personId Then
                travellerSearchContext.SelectedTravellers.Remove(traveller)
                Exit For
            End If
        Next
        context.Session("PersonSearchContext") = personSearchContext
    Case "Save"
         bookingContext.Travellers = personSearchContext.SelectedTravellers
         context.Session("BookingContext") = bookingContext                 
End Select

The issue is the Travellers collection within the object “BookingContext” is being updated when I add and remove from the collection within “PersonSearchContext”. It’s as though there is some sort of link or pointer between them.

Any ideas?

Cheers.

Answer 1

The problem is this line in your Save code:

bookingContext.Travellers = personSearchContext.SelectedTravellers

What you’re doing there is taking the reference to the SelectedTravellers collection in the personSearchContext object and assigning the reference to the Travellers collection in the bookingContext object. This assignment means that bookingContext.Travellers is no longer a separate collection from personSearchContext.SelectedTravellers. They’re now both references to the same object in memory.