Hello, world !

I have a question about this code,
it's a code for generating a random string (of 10 digits)
so I can use it to create random passwords. I use this for all my passwords.

It works great, the code.

Code:
Public Class Form1
    Private Function GenerateString(ByVal length As Integer, ByVal content As Integer, ByVal casing As Integer) As String
        Dim r, r1, r2 As New Random
        Dim gString As String = String.Empty
        Dim LowAlph As String = "abcdefghijklmnopqrstuvwxyz"
        Dim UppAlph As String = LowAlph.ToUpper
        Dim addLetter As Char
        Do Until gString.Length = length
            Select Case casing
                Case 0
                    Select Case r.Next(0, 2)
                        Case 0
                            addLetter = LowAlph.Substring(r1.Next(0, 25), 1)
                        Case 1
                            addLetter = UppAlph.Substring(r1.Next(0, 25), 1)
                    End Select
                Case 1
                    addLetter = UppAlph.Substring(r1.Next(0, 25), 1)
                Case 2
                    addLetter = LowAlph.Substring(r1.Next(0, 25), 1)
            End Select
            Select Case content
                Case 0
                    Select Case r.Next(0, 2)
                        Case 0
                            gString &= addLetter
                        Case 1
                            gString &= r1.Next(0, 9)
                    End Select
                Case 1
                    gString &= r1.Next(0, 9)
                Case 2
                    gString &= addLetter
            End Select
        Loop
        Return gString
    End Function
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox1.Text = GenerateString(TextBox2.Text, 0, 0)
    End Sub
End Class
But I see somewhere in the code (on the 3rd line)

Code:
Dim r, r1, r2 As New Random
but r2 isn't used everwhere else in the code.
Is r2 not nessecary(sp) ? Can I discard it, end delete from code ?

I want to write (this)code as clean(short) as possible, so it uses minimum
memory/cpu!

I'm beginning to become a beginner, so please explain in simple.

why this code doesn't use the variable r2
is this code actually random ? that's what I wanna know.
And I thank you.

bye