VB Streamwriter设置为ISO-8859-1，但文件获取UTF8-无Bom编码

Question

I have a problem i set the streawriter to write ISO-8853-1 but the file gets utf8 encoding. See code below:

when declaring str i set it to iso-8853-1 and when i check the output files encoding i get UTF8-without bom.

Imports System.Text
Imports System.IO

Module Module1

Sub Main()
    Using str = New StreamWriter("C:\blabla.txt", False, encoding.GetEncoding("ISO-8859-1"))
        str.Write("23124124AÖ")
        Dim encoding = str.Encoding
        str.Close()
    End Using

    Dim currentEncoding = GetFileEncoding("C:\blabla.txt")
End Sub
    Public Function GetFileEncoding(filePath As String) As Encoding
        Using sr As StreamReader = New StreamReader(filePath, True)
            sr.Read()
            Return sr.CurrentEncoding
        End Using
    End Function
End Module

Answer 1

There's a reason that you have to pass encodings to the constructors of both readers and writers. Files, in and of themselves, don't have encodings. They're just a collection of bytes.

It's up to you , be selecting an encoding, to say what interpretation you want to place on those bytes. You opened the StreamReader without specifying an encoding and so it defaults to UTF-8.