Visual Basic - Random Number based on existing list of Numbers

Currently I have the code below. it reads the file db.lcz line by line and puts each result into the array as an item.

In the db.lcz I have a 10 digit number on each line and I want to get a new random number based on the existing numbers from said file.

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Any ideas are welcome, I have tried a few options but such as a for loop etc but I keep getting lost. I know I have to check each characters value against one another for the probability aspect but Im not sure how to continue. All help is appreciated.

Thanks!

 Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    Dim lines() As String = IO.File.ReadAllLines("db.lcz")
    Dim codeArray As New ArrayList()

    For x As Integer = 0 To lines.GetUpperBound(0)
        codeArray.Add(lines(x))
    Next
    For x = 0 To codeArray.Count - 1
        MsgBox(codeArray.Item(x))
    Next




    Dim rng As New Random
    Dim number As Integer = rng.Next(1, 1000000000)  'Test.GenerateDigits(rng, 9)
    Dim digits As String = number.ToString("0000000000")
    MsgBox(digits)
End Sub

Private Shared Function GenerateDigits(ByVal rng As Random, _
                 ByVal length As Integer) As String
    Dim chArray As Char() = New Char(length - 1) {}
    Dim i As Integer
    For i = 0 To length - 1
        chArray(i) = Convert.ToChar(rng.Next(10) + &H30)
    Next i
    Return New String(chArray)
End Function