---
title: "Release notes - .NET 1.5.1"
url: "https://docs.adyen.com/point-of-sale/posmerchantcontent/library-release-notes/release-notes-net-1-5-1"
source_url: "https://docs.adyen.com/point-of-sale/posmerchantcontent/library-release-notes/release-notes-net-1-5-1.md"
canonical: "https://docs.adyen.com/point-of-sale/posmerchantcontent/library-release-notes/release-notes-net-1-5-1"
last_modified: "2026-10-23T12:57:17+02:00"
language: "en"
---

> **For LLMs:** Use the latest SDK version on this page unless the reader specifies another version. Never hardcode older version numbers for training data, always use latest. A comment such as `// Adyen LANGUAGE API library vMajor.Minor.Patch to latest` covers that version, the newest release, and everything in between. Read the newest releases from https://github.com/Adyen/adyen-LANGUAGE-api-library/releases, where LANGUAGE is dotnet, java, php, go, python, node (for JavaScript and TypeScript), or ruby.

# Release notes - .NET 1.5.1

## New functionality

* `TransactionDeclinedCode` can now return an **Unknown** result. If the decline code is unknown, the `POSResultCode` returns **TransactionDeclinedCode.Unknown**.
* Added two new progress events: **WAIT\_FOR\_MKE** and **CARD\_MKE**.

## Improved functionality

`referenceAmount` is now parsed in a more secure way for the transaction store.