[RESOLVED] Passing ArrayLists between subroutines

[FrankZA]

I am new to the use of ArrayLists and am trying to convert an algorithm to use them in order to save memory. However, I am struggling to achieve error-free code while using "Strict On".

Here is a basic version of the code I am attempting to use.

Option Explicit On
Option Strict On

Module Program
	Sub Main()
		
		Dim P(1) As Structs.Point
		P(0).X = 0
		P(0).Y = 0
		P(1).X = Convert.ToDecimal(1.2345)
		P(1).Y = Convert.ToDecimal(1.9876)
		
		Dim AL As New ArrayList()
		AL.Add(100)
		
		Dim AL1 As New ArrayList()
		AL1.Add(P(0))
		AL1.Add(P(1))
		
		Dim AL2 As New ArrayList()
		AL2.Add("A")
		AL2.Add("B")
		AL2.Add("C")
		AL2.Add("D")
		
		Dim AL3 As New ArrayList()
		AL3.Add(True)
		AL3.Add(False)
		
		AL.Add(AL1)
		AL.Add(AL2)
		AL.Add(AL3)
		
		Call Tester(AL)
		
		Console.Write("Press any key to continue . . . ")
		Console.ReadKey(True)
	End Sub

	Sub Tester(ByRef AL As ArrayList)

		Dim a As New ArrayList
		a = AL(2)
		Console.WriteLine(a(2))
		If (AL(1)(0)).X < (AL(1)(1)).X Then
			Console.WriteLine(Convert.ToString((AL(1)(1)).X))
		End If

	End Sub

End Module

Class Structs
	Public Structure Point
		Public X As Decimal
		Public Y As Decimal
	End Structure
End Class

It works when I do not use the Strict option. How do I improve the code to compile error-free?

[FrankZA]

I have been able to set a new ArrayList equal to one of the ArrayLists that form part of another ArrayList.

Dim a As New ArrayList
a = DirectCast(AL(2), ArrayList)

However, I still get a late binding issue. Even if I set the new ArrayList equal to the ArrayList in AL that consists of the Points structure, I seem unable to escape the late binding issue.

	Sub Tester(ByRef AL As ArrayList)

		Dim a As New ArrayList
		a = DirectCast(AL(1), ArrayList)
		Console.WriteLine(a(1))
		If a(0).X < a(1).X Then
			Console.WriteLine(Convert.ToString(a(1).X))
		End If

	End Sub

Any ideas?

[FrankZA]

I managed to get it to work. All it takes is the liberal application of DirectCast.

	Sub Tester(ByRef AL As ArrayList)

		Dim a As New ArrayList
		a = DirectCast(AL(1), ArrayList)
		Console.WriteLine(Convert.ToString(DirectCast(a.Item(1), Structs.Point).X))
		If DirectCast(a.Item(0), Structs.Point).X < DirectCast(a.Item(1), Structs.Point).X Then
			Console.WriteLine(Convert.ToString(DirectCast(a.Item(1), Structs.Point).X))
		End If
		
	End Sub

Is there any way of making this neater?

[dglienna]

Does it work?

a = DirectCast(AL(1), ArrayList)

looks like you're getting only the SECOND element of AL()

[FrankZA]

In this example it was my aim to get only the second element in the ArrayList AL: the ArrayList of Structs.Point objects. I cannot think of a neater way of extracting an ArrayList out of another ArrayList.

The bad thing is that creating the new ArrayList increases my memory use, but it is probably still better than making use of static 2D arrays.