public void WriteExtension(PlainBufferExtension extension) { WriteTag(PlainBufferConsts.TAG_EXTENSION); output.WriteRawLittleEndian32(PlainBufferBuilder.ComputeSkipLengthForExtensionTag(extension)); int extensionCount = 0; if (extension.HasSeq()) { WriteSequenceInfo(extension.GetSequenceInfo()); extensionCount++; } if (extensionCount == 0) { throw new IOException("no extension tag is Writen."); } }