Question

In a project I’ve recently taken over, there is a call to a function which does some calculations; this is called in a row, several times (between 1 and 10 times usually).

While dr.read  ‘depending on a db call, loop 1 or more times
 Dim calc As New CalcClass
 Dim newDoStuff As New System.Threading.Thread(New System.Threading.ParameterizedThreadStart(AddressOf DoStuff))
 newDoStuff.Start(calc)
End while

Private Sub DoStuff(ByVal calc As Object)
‘do something that takes between 5-10 seconds
End sub

In order to speed this up, i am trying to add asynchronous processing (see above example), this works in my code, all tasks are done at the same time, but what I don’t understand is how to then wait for all these threads to finish (there is no set amount of threads, it can be between 1 and 10 depending on some other data) before finishing up with a final task that needs to run after all tasks are completed.

Can anyone suggest a way to do this – I’m looking for an easy way to basically say “O.k, all tasks are finished at this point, call another task”

Cliffs

• Several tasks need to run at the same time (between 1 and 10)
• Each task takes several seconds
• Code currently works – it does them all at the same time
• Once all tasks (between 1-10) are
  finished, fire off some other code (only when all tasks are finished) – stuck on best method to do the following

Answer 1

Put all your thread in an List

Dim threads As new List(Of System.Threading.Thread)

While dr.read  ‘depending on a db call, loop 1 or more times
    Dim calc As New CalcClass
    Dim newDoStuff As New System.Threading.Thread(New System.Threading.ParameterizedThreadStart(AddressOf DoStuff))
    threads.Add(newDoStuff)
    newDoStuff.Start(calc) 
End while

finally join all your threads

For Each thread In threads Do
    thread.Join()
Next