Nest ForEach Loops don't update object

I have come across this issue multiple times, and I'm sure it has something to do with my lack of understanding. If someone would be kind enough to explain the problem and why it doesn't do what I expect, and how to properly frame the code, I would greatly appreciate it. I cut out sections but you should be able to understand what I'm doing.

I have a ForEach loop nested inside another ForEach loop, the inside nest, although it appears to successfully iterate through the object, won't update it? I use watches, breakpoints, ... it all shows fine, the variable time is updating correctly and has the correct value. The current_pvt is correct, the current_move is correct, but after the call

current_pvt.time = time

I check the current_pvt.time value and it's the same as it was previous to the assignment or the same as the current_pvt.time value for the previous current_move? I can't tell for sure as they are the same prior to the statement. Memory serves from earlier attempts on different code that is writes it with the first current_move value.

What gives? I have seen this while writing this nested ForEach so apparently I am doing something fundamentally wrong. Typically the first time through the inner loop it updates correctly, but the following times, it does not, so I assume it has to do with the object not be updated, destroyed, renewed properly? How should I write a nested ForEach Loop like this with two different objects?

Thank you,

Kennard

Public Class _program
    Public programname As String
    Public moves As List(Of _move)

    Public Sub New()
        progglobals = New _globals
        moves = New List(Of _move)
    End Sub

End Class

Public Structure PVT
    Public X As Double
    Public Y As Double
    Public Xvel As Double
    Public Yvel As Double
    Public time As Double
End Structure

Public Class _move
    Public moveID As Integer
    Public pvtPts As New List(Of PVT)
    Public timeslice As Double
End Class

 Private Sub SetPVTTimes(ByRef current_program As Prog._program)
        Dim time As Double = 0.0

        For Each current_move As Prog._move In current_program.moves
            If current_move.pvtPts.Count = 0 Then
               time = 0.0
            Else
                For Each current_pvt As Prog.PVT In current_move.pvtPts
                    current_pvt.time = time
                    time = time + current_move.timeslice
                Next
            End If
        Next
    End Sub

Tags: Visual Basic