Passing two-dimensional array through functions

Question

I have interesting situation with passing two-dimensional array through functions.
Array is declared at form's level scope:
I try to rewrite a part of my code from VB6 where I have workable example.

Dim myArray(,) As Double

Then I get a sub where array is redimed and filled according to data, something like this, symbolic situation:

Public Sub mySub(ByVal myArray(,) As Double)

    Dim temparray() As Double = {3, 5, 7, 9}
    For a As Double = 0 temparray.length - 1
         ReDim Preserve myarray(2, temparray(a))
    Next a

    myArray(1, 5) = 3.14
    ... etc...
End Sub

And finally, I would like to fill and read data in array from other sub:

mySub(myArray)
Debug.Print(myArray(1, 5))

And here I get error message:

Object reference not set to an instance of an object.

Data in mySub is filled properly but I can't see this data in calling sub.
What do I do wrong and how can I get this scenario working?

In VB.NET try to get rid of your multidimensional/jagged arrays. In most cases you can replace them with something more readable,less error-prone and more expandable like a List(Of CustomClass). — Tim Schmelter
– Tim Schmelter, Commented Jan 24, 2013 at 12:12

Antonio · Accepted Answer · 2013-01-24 12:19:10Z

11

You can solve it by doing this:

Public Sub mySub(ByRef myArray(,) As Double)
    '...
End Sub

You need to reference the variable in order to have the changes outside the Sub.

answered Jan 24, 2013 at 12:19

Antonio

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