خطای invalid برای کد system.io در vb 6

سلام می خوام با استفاده از کد زیر یک کانور تور بنویسم ولی به همه کد های سیستم خطا می گیرید، ایا برنامه ام مشکل دارد، تریال بودن ان ممکنه ایجاد مشکل کند با تشکر

' Currency Convert

' By Aziz S. Hussain
' http://www.azizsaleh.com
' [email protected]

' Licensed under the LGPL license

Imports System.IO
Imports System.Text.RegularExpressions
Public Class currency

Private Sub USD_Click()
' Need the scraping
Dim Str As System.IO.Stream
Dim srRead As System.IO.StreamReader
Dim strAmount As String

strAmount = currencyAmount.Text

' Get values from the textboxes
Dim strFrom() As String = Split(currencyFrom.Text, " - ")
Dim strTo() As String = Split(currencyTo.Text, " - ")

' Web fetching variables
Dim req As System.Net.WebRequest = System.Net.WebRequest.Create("http://www.xe.com/ucc/convert.cgi?Amount=" + strAmount + "&From=" + strFrom(1) + "&To=" + strTo(1) + "YER&image.x=47&image.y=19&image=Submit")
Dim resp As System.Net.WebResponse = req.GetResponse

Str = resp.GetResponseStream
srRead = New System.IO.StreamReader(Str)

' Match the response
Try
Dim myMatches As MatchCollection
Dim myRegExp As New Regex("([0-9]+.[0-9]+ " + strTo(1) + ")")

myMatches = myRegExp.Matches(srRead.ReadToEnd)

' Search for all the words in the string
Dim sucessfulMatch As Match
For Each sucessfulMatch In myMatches
mainText.Text = sucessfulMatch.Value
Next
Catch ex As Exception
mainText.Text = "Unable to coect to XE"
Finally
' Close the streams
srRead.close()
Str.Close()
End Try
convertToLabel.Text = strAmount + " " + strFrom(0) + " Converts To: "
End Sub
Private Sub convertButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles convertButton.Click
' Check if the currency is a number
If Not IsNumeric(currencyAmount.Text) Then
MsgBox("Please enter a valid amount!", MsgBoxStyle.Information, "Invalid Input")
currencyAmount.Focus()
Retu
End If

doCalculate()
End Sub

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
currencyFrom.SelectedIndex = 0
currencyTo.SelectedIndex = 1
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
MsgBox("Simple Currency Converter By Aziz S. Hussain", MsgBoxStyle.Information, "www.AzizSaleh.com")
End Sub
End Class