CharsetFilter Class

public class CharsetFilter : MimeFilterBase

                    public static string ConvertToUtf8 (Stream input, string charset)
{
    using (var memory = new MemoryStream ()) {
        using (var filtered = new FilteredStream (memory)) {
            // Convert the text from the source charset to UTF-8 while it is being copied.
            filtered.Add (new CharsetFilter (charset, "utf-8"));

            // Normalize the line endings to Unix-style LF line endings as well.
            filtered.Add (new Dos2UnixFilter ());

            input.CopyTo (filtered);
            filtered.Flush ();
        }

        return Encoding.UTF8.GetString (memory.GetBuffer (), 0, (int) memory.Length);
    }
}