Not all developers know that VB6 permits to dynamically change the rank (i.e. the number of dimensions) of an array, as in this code snippet:

' this array can have 1 or 2 dimensions
Dim arr() As Integer
       
Sub InitArray(rank As Integer)
   Dim i As Integer, j As Integer
        
   If rank = 1 Then
      ReDim arr(100) As Integer
      For i = 1 To UBound(arr)
         arr(i) = i
      Next
   Else
      ReDim arr(100, 20)
      For i = 1 To UBound(arr, 1)
         For j = 1 To UBound(arr, 2)
            arr(i, j) = i * j
         Next
      Next
   End If
End Sub

VB.NET doesn’t allow you to change the rank of an array, therefore the converted VB.NET code would raise one instance of the following error:

Number of indices exceeds the number of dimensions in the indexed array

for each statement where the array is accessed with two indexes. These is no definitive solution to this problem, however VB Migration Partner allows you to significantly decrease the number of this compilation error, using a combination of pragmas:

    '## ParseReplace Dim arr() As Integer, arr2() As Integer
    Dim arr() As Integer
    '## arr2.ArrayRank 2
    '## PreProcess "arr(?=\([^,)]+,[^,)]+\))", "arr2"
    '## PreProcess "(?<=(LBound|UBound)\()arr(?=,)", "arr2"


An explanation of each pragma is in order. The ParseReplace pragma causes VB Migration Partner to realize that there are actually two arrays (arr and arr2) and the ArrayRank pragma specifies that arr2 is a 2-dimensional array. The first subsequent PreProcess pragma changes arr into arr2 if the array reference is followed by two indexes that are separated by a comma – as in arr(1,2)  - whereas the second PreProcess pragma changes array references that appear in LBound and UBound method calls. The result is this piece of error-free VB.NET code:

Private arr() As Short
Private arr2(,) As Short
    
Public Sub InitArray(ByRef rank As Short)
   Dim i As Short
   Dim j As Short
        
   If rank = 1 Then
      ReDim arr(100)
      For i = 1 To UBound6(arr)
         arr(i) = i
      Next
   Else
      ReDim arr2(100, 20)
      For i = 1 To UBound6(arr2, 1)     
         For j = 1 To UBound6(arr2, 2)
            arr2(i, j) = i * j
         Next
      Next
   End If
End Sub

This approach isn't bulletproof, though. In fact, it works only for array occurrences whose indexes aren't function calls. For example, it doesn't work in the following case:

      arr( GetIndex(1), GetIndex(2) )

However,  you can easily take care of these residual errors by means of additional ParseReplace or PreProcess pragmas.