VB.NET 4.0 Parallel.ForEach AddressOf Multiple Values?

Question

I am trying change from Delegates to Parallel.ForEach

I see the below works fine.

Imports System.Threading.Tasks

  Sub Main()
   Dim secs() As Integer = {2, 3, 1}
   Parallel.ForEach(secs, AddressOf Method2)
  End Sub

  Sub Method2(ByVal i As Integer)
   Console.WriteLine(i.ToString)
  End Sub

But what if my Sub takes more then one variable? Can you show me how I should do the below?

Imports System.Threading.Tasks
  Sub Main()
   Dim secs() As Integer = {2, 3, 1}
   Dim Path as String = "Constant"

   Parallel.ForEach(secs, Path, AddressOf Method2)
  End Sub

 Sub Method2(ByVal i As Integer, path as string )
  Console.WriteLine(i.ToString, path)
 End Sub

Thank you

Answer 1

You can do this via a Lambda Expression:

Imports System.Threading.Tasks
  Sub Main()
   Dim secs() As Integer = {2, 3, 1}
   Dim Path as String = "Constant"

   Parallel.ForEach(secs, Sub(sec) Method2(sec, Path))
  End Sub

 Sub Method2(ByVal i As Integer, path as string)
  Console.WriteLine(i.ToString(), path)
 End Sub

This will allow the compiler to create a closure that gets the value of Path, and pass it directly into your method.

Answer 2

Certainly in C#, I'd use a lambda expression to call Method2 instead:

Parallel.ForEach(secs, i => Method2(i, path));

Whether the equivalent will look elegant in VB is beyond the amount of good judgement I have about a language I don't use at 12.50am, but you don't have a lot of other choices really - assuming you don't want to create an instance of another class, passing path into the constructor, and then using a single-parameter method in that class...

(Oh, and another option would be to change Method2 into a single parameter method where the parameter encapsulated both values. So I guess you do have a few options - but in C# at least, the lambda expression one would be the way to go.)