一个vb的小疑点

一个vb的小问题
本人不懂vb，在做报表的时候要用，Public Function FixSpelling(ByVal str As String) As String
  Dim arrys() As String = Split(str,",") 
  Dim i As Integer
  For i = 0 To arrys.Length- 1 Step i + 1
If i<> 0 Then
If i % 9 = 0 Then
arrys(i) = arrys(i) + vbNewLine
End If
End If
  Next
  str = String.Join(arrys,",")
End Function
这个函数的作用是一个用逗号分隔的字符串，如aa,bb,cc,dd,ee,ff,gg，在指定的逗号分隔处
加上换行符，老是报错，晕菜了，请高手指点一下


------解决方案--------------------

VB code

Public Function FixSpelling(ByVal str As String) As String
    Dim arrys() As String
    arrys = Split(str, ",")'<-1
    Dim i As Long
    For i = 0 To UBound(arrys) 'Step 1 '<-2
    If i <> 0 Then
        If (i Mod 9) = 0 Then '<-3
              arrys(i) = arrys(i) & vbNewLine
        End If
    End If
    Next
    str = Join(arrys, ",") '<-4
End Function