Problème encodage avec google translator

Bonjour, je recupère des traductions à partir de google Translator. Mon problème c'est que la traduction récupérée ne reconnait pas certains caractère malgrè l'utilisation de UTF-8. Voici un bout de code:

Code:

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Public Sub New()
        MyBase.New("Google Translator", "http://translate.google.com/translate_t", New String(,) {{"ar", "en"}, _
{"zh", "en"}, {"zh-CN", "zh-TW"})
        End Sub

 Public Overrides Function GetPostData(ByVal inputLanguage As String, ByVal outputLanguage As String, ByVal [text] As String) As String
        Return "text=" + Encode(text) + "&sl=" + inputLanguage + "&tl=" + outputLanguage
        End Function

Protected Overridable Function GetTranslation(ByVal inputLanguage As String, ByVal outputLanguage As String, ByVal innerText As String) As String
            Return innerText
        End Function

 Public Overrides Function Translate(ByVal inputLanguage As String, ByVal outputLanguage As String, ByVal [text] As String) As String
            Dim toReturn As String = ""
 Dim innerText As String = Me.GetInnerText(Me.GetPostData(inputLanguage, outputLanguage, [text]))
                toReturn = Me.GetTranslation(inputLanguage, outputLanguage, innerText)
......
  Dim utfS As Encoding = System.Text.Encoding.ASCII 
            Dim utfD As Encoding = System.Text.Encoding.UTF8 
            Return (utfD.GetString(Encoding.Convert(utfS, utfD, utfS.GetBytes(toReturn))))
 End Function

Le problème se situe au niveau de la traduction que retourne la fonction Translate (toReturn).
Pouvez-vous m'aider?