在递归创建时，如何判断所有线程何时完成？

Question

简介 目前我有一个子程序，我需要递归调用。我每次需要它时都会在一个单独的线程中调用它。例如：

Private Sub process_part_for_tkv(ByVal a As String, ByVal b As Integer, ByVal c As Integer, ByVal d As String)

'Do stuff
For Loop 'sudo code just to show a loop is used

   Dim process_part_for_tkv_thread As New Threading.Thread(Sub() process_part_for_tkv(newa, newb, newc, newd))
   process_part_for_tkv_thread.IsBackground = True
   process_part_for_tkv_thread.Priority = Threading.ThreadPriority.Highest
   process_part_for_tkv_thread.Start()    
Next

End Sub

然后我会调用初始子来运行：

   Dim process_part_for_tkv_thread As New Threading.Thread(Sub() process_part_for_tkv(newa, newb, newc, newd))
   process_part_for_tkv_thread.IsBackground = True
   process_part_for_tkv_thread.Priority = Threading.ThreadPriority.Highest
   process_part_for_tkv_thread.Start() 

问题

线程工作正常但我怎么能告诉我的所有线程何时运行完毕？有没有办法跟踪这个？