Write text files without Byte Order Mark (BOM)?

In order to omit the byte order mark (BOM), your stream must use an instance of UTF8Encoding other than System.Text.Encoding.UTF8 (which is configured to generate a BOM). There are two easy ways to do this:

1. Explicitly specifying a suitable encoding:

1. Call the UTF8Encoding constructor with False for the encoderShouldEmitUTF8Identifier parameter.

2. Pass the UTF8Encoding instance to the stream constructor.

' VB.NET:
Dim utf8WithoutBom As New System.Text.UTF8Encoding(False)
Using sink As New StreamWriter("Foobar.txt", False, utf8WithoutBom)
    sink.WriteLine("...")
End Using

// C#:
var utf8WithoutBom = new System.Text.UTF8Encoding(false);
using (var sink = new StreamWriter("Foobar.txt", false, utf8WithoutBom))
{
    sink.WriteLine("...");
}

2. Using the default encoding:

If you do not supply an Encoding to StreamWriter‘s constructor at all, StreamWriter will by default use an UTF8 encoding without BOM, so the following should work just as well:

' VB.NET:
Using sink As New StreamWriter("Foobar.txt")
    sink.WriteLine("...")
End Using

// C#:
using (var sink = new StreamWriter("Foobar.txt"))
{
    sink.WriteLine("...");
}

Finally, note that omitting the BOM is only permissible for UTF-8, not for UTF-16.