Conectar sql en una clase separada

Imports System.Data.SqlClient
Imports System.IO

Public Class SqlCon

    Public sql As SqlConnection
    Public str As String = ""

    Public Sub sqlOpen()
        str = StringConex()
        sql = New SqlConnection(str)
        sql.Open()
    End Sub

    Public Sub sqlClose()
        sql.Close()
        sql.Dispose()
    End Sub

    Public Function StringConex() As String
        Dim rd As New StreamReader("conex.txt")
        Dim linea As String = rd.ReadLine()
        rd.Close()
        rd.Dispose()
        Return linea
    End Function
End Class

Public Class Form1
Private Sub btn_ok_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn_ok.Click
        Dim con As New SqlCon
        Try
            con.sqlOpen()
            MessageBox.Show("Conexión OK!")
            con.sqlClose()
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
End Sub
End Class