Better Alternative to Arraylist.Contains

[ayozzhero@gmail.com-3]

        [COLOR="Navy"]Dim[/COLOR] a [COLOR="Navy"]As String[/COLOR](,) = mPermutation.Permutations("123456789")
        [COLOR="Navy"]Dim [/COLOR]n1 [COLOR="Navy"]As Integer[/COLOR] = a.GetUpperBound(0)
        [COLOR="Navy"]Dim [/COLOR]n2 [COLOR="Navy"]As Integer[/COLOR] = a.GetUpperBound(1)
        [COLOR="Navy"]Dim [/COLOR]al [COLOR="Navy"]As New[/COLOR] ArrayList
        [COLOR="Navy"]Dim [/COLOR]s [COLOR="Navy"]As String[/COLOR] = ""
        [COLOR="Navy"]For [/COLOR]i1 [COLOR="Navy"]As Integer[/COLOR] = 0 [COLOR="Navy"]To[/COLOR] n1
            [COLOR="Navy"]For [/COLOR]i2 [COLOR="Navy"]As [/COLOR][COLOR="Navy"]Integer [/COLOR]= 0 To n2
                [COLOR="Navy"]If Not[/COLOR] al.Contains(a(i1, i2)) [COLOR="Navy"]Then[/COLOR]
                    al.Add(a(i1, i2))
                [COLOR="Navy"]End If[/COLOR]
            [COLOR="Navy"]Next[/COLOR]
        [COLOR="Navy"]Next[/COLOR]

The line which contains: If Not al.Contains(a(i1, i2)) Then works very slow. What I want is just to make the array/arraylist unique. Is there any other way I can achieve this?

By the way, I can no longer log in using my previous ID: ayozzhero, even my email is no longer recognized.