Как автоматически определить кодировку при открытии текстового файла?

            If Kodirovka = "Utf8-Anci" Then
                RTB.LoadFile(FilePath, RichTextBoxStreamType.PlainText)
            ElseIf Kodirovka = "Unicode" Then
                RTB.Text = IO.File.ReadAllText(FilePath, Encoding.Unicode)
            Else 'utf8 bom
                RTB.Text = IO.File.ReadAllText(FilePath, Encoding.UTF8)
            End If

RTB.Text = IO.File.ReadAllText(FilePath, Encoding.Default)

Dim bt() As Byte = File.ReadAllBytes("C:\01\_anci.txt")
Dim Txt As String = String.Empty
If bt(0) = 255 AndAlso bt(1) = 254 Then
    Txt = Encoding.Unicode.GetString(bt)
ElseIf bt(0) = 239 AndAlso bt(1) = 187 And bt(2) = 191 Then
    Txt = Encoding.UTF8.GetString(bt)
Else
    Txt = Encoding.Default.GetString(bt)
End If
RichTextBox1.Text = Txt

Dim _unicode As Encoding = Encoding.Unicode
Dim preamble As Byte() = _unicode.GetPreamble()
Dim _utf8 As Encoding = Encoding.UTF8
Dim preamble8 As Byte() = _utf8.GetPreamble()

Function GetStreamReader(ByVal path) As StreamReader
    Dim stream As FileStream = Nothing
 
    Try
        stream = File.OpenRead(path)
 
        Dim fileEncoding As Encoding = Encoding.UTF8
        Dim detector As New CharsetDetector
        detector.Feed(stream)
        detector.DataEnd()
        If detector.Charset IsNot Nothing Then
            fileEncoding = Encoding.GetEncoding(detector.Charset)
        End If
 
        stream.Position = 0
        Return New StreamReader(stream, fileEncoding)
    Catch
        If stream IsNot Nothing Then stream.Close()
 
        Throw
    End Try
 
End Function