Question

I wrote the following code:

Public Class Form1

Private Structure udtThing
    Dim SomeText As String
    Dim SomeElements() As String
    Public Shared Function CreateInstance() As udtThing
        Dim result As New udtThing
        result.SomeText = String.Empty
        ReDim result.SomeElements(2)
        result.SomeElements(0) = String.Empty
        result.SomeElements(1) = String.Empty
        result.SomeElements(2) = String.Empty
        Return result
    End Function
End Structure

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    Dim nThings() As udtThing
    nThings = Array.CreateInstance(GetType(udtThing), 10)

End Sub
End Class

I partly works, nThings becomes an array of 11 udtThings.
But .SomeElements is not redimmed to 3 strings of String.Empty, but it is “Nothing” instead.

Does anybody see where I went wrong?

Thank you very much!

Answer 1

By design, a Redim is required. Array.CreateInstance() isn’t going to perform that operation, it can’t guess what size is required. You’ll have to help:

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Dim nThings(10) As udtThing
    For ix As Integer = 0 To UBound(nThings)
        nThings(ix) = udtThing.CreateInstance()
    Next
End Sub