Membuat Penomoran Otomatis di vb.net 2008

Public Function autonumber()
        Dim query As String
        Dim xmyread As SqlDataReader
        Dim xmycmd As SqlCommand
        Dim nilaiawal, nilaiauto, nilaiakhir As String



        query = "select nim from mahasiswa order by nim desc"
        xmycmd = New SqlCommand(query, mycn)
        xmyread = xmycmd.ExecuteReader
        If xmyread.HasRows = True Then
            xmyread.Read()
            nilaiawal = xmyread.Item("NIM")
            nilaiauto = Val(Mid(xmyread.Item("nim"), 4, 7)) + 1
            nilaiakhir = "nim" & Right("0000000", 7 - nilaiauto.Length) & nilaiauto
        Else
            nilaiakhir = "NIM0000001"
        End If
        xmyread.Dispose()
        Return nilaiakhir

    End Function



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