Fortify scan Null Dereference issue at For Each loop VB.NET

Question

Our application is written in VB.Net. On scanning our application in HP Fortify, Null Dereference issue was pointed at the only the For Each ... Next loop in the few pages. What could be the reason the Null Reference is shown only at the For each loop. At all places where the For Each loop is used in the application the null dereference is pointing to the "Next" of the For Each loop. Please help resolve this scan issue. A sample code snippet from our application is below.

If Request.QueryString("mode") IsNot Nothing Then
                        mode = Request.QueryString("mode")
                    End If
                    .
                    .
                    .
                    For Each col In gridTemp.Columns
                        Select Case col.HeaderText
                            Case "ID"
                                col.Visible = IIf(mode = "Admin", True, False)
                            Case "Name"
                                col.Visible = IIf(mode = "Admin", True, False)
                            Case "Balance"
                                col.Visible = IIf(mode = "Admin", False, True)
                            Case "Dues"
                                col.Visible = IIf(mode = "Admin", True, False)
                            Case "Contact"
                                col.Visible = IIf(mode = "Admin", False, True)
                        End Select
                    Next

Answer 1

The only way we've found to get around this is to convert for each loops into for loops. In this case, try using something like

For I as Integer = 0 to gridTemp.Columns.Count - 1  
 Dim col as Column(i)  
 Select Case col.HeaderText  

 Case "ID"  
      col.Visible = IIf(mode = "Admin", True, False)  
 Case "Name"  
      col.Visible = IIf(mode = "Admin", True, False)  
 Case "Balance"  
      col.Visible = IIf(mode = "Admin", False, True)  
 Case "Dues"  
      col.Visible = IIf(mode = "Admin", True, False)  
 Case "Contact"  
      col.Visible = IIf(mode = "Admin", False, True)  
 End Select  
Next