>Is there a way to optimize this method?
>
>

>        ' Equivalent of the AT() function in VFP
>        ' expC1 Search for
>        ' expC2 Search string
>        ' expN1 Occurence
>        ' expN2 Mode
>        Public Function At(ByVal tcSearchFor As String, ByVal tcSearchIn As String, _
>         ByVal tnOccurence As Integer, ByVal tnMode As Integer) As Integer
>            Dim lnCounter As Integer = 0
>            Dim lnLocation As Integer = 0
>            Dim lnOccured As Integer = 0
>
>            ' In this case we actually have to locate the occurence
>            If tnMode = 1 Then
>                lnLocation = 0
>            Else
>                lnLocation = tcSearchIn.Length
>            End If
>
>            ' Loop through the string and get the position of the required occurence
>            For lnCounter = 1 To tnOccurence
>
>                If tnMode = 1 Then
>                    lnLocation = tcSearchIn.IndexOf(tcSearchFor, lnLocation)
>                Else
>                    lnLocation = tcSearchIn.LastIndexOf(tcSearchFor, lnLocation)
>                End If
>
>                If lnLocation < 0 Then
>                    Exit For
>                Else
>
>                    ' Increment the occured counter based on the current mode we are in
>                    lnOccured = lnOccured + 1
>
>                    ' Check if this is the occurence we are looking for
>                    If lnOccured = tnOccurence Then
>                        Return lnLocation + 1
>                    Else
>                        If tnMode = 1 Then
>                            lnLocation = lnLocation + 1
>                        Else
>                            lnLocation = lnLocation - 1
>                        End If
>                    End If
>
>                End If
>
>            Next
>
>            Return 0
>        End Function
>

>
>The reason I ask is that I thought if using a StringBuilder would be better here. This is considering that I have some string of up to 20k to be passed here. so, if tcSearchFor is 20k, could this be a factor?

I don't see where a stringbuilder could help. You are passing in two strings neither of which are modified by the method.....