System.Text.UTF32Encoding.GetPreamble C# (CSharp) Method

        public override byte[] GetPreamble()
        {
            throw null;
        }

        public void OpensReaderWithAutoDetectEncoding()
        {
            string expected = "test";
            Encoding utf32 = new UTF32Encoding(false, true);
            byte[] resourceData = GetBytes(expected, utf32);
            resourceData = (byte[])ArrayUtils.Concat(utf32.GetPreamble(), resourceData);
            EncodedResource r = new EncodedResource( new InputStreamResource( new MemoryStream( resourceData), "description" ), Encoding.UTF8, true);
            StreamReader reader = (StreamReader)r.OpenReader();
            Assert.AreEqual(Encoding.UTF8.EncodingName, reader.CurrentEncoding.EncodingName);
            string actual = reader.ReadToEnd();
            Assert.AreEqual( "\uFEFF" + expected , actual);
// interestingly the line below is *not* true!
//            Assert.AreEqual(utf32.GetString(resourceData), actual);
            Assert.AreEqual(utf32, reader.CurrentEncoding);
        }