var list = Encoding.GetEncodings();
using (var sw = new StreamWriter("Decoding.txt", false, Encoding.Default))
{
    foreach (var encoding in list)
    {
          sw.WriteLine($"[{encoding.Name}]: '{encoding.GetEncoding().GetString(buffer)}'");                           
          sw.WriteLine(Environment.NewLine);
          sw.WriteLine(Environment.NewLine);
    }
 }