OPC UA .NET Stack

Overview

This OPC UA reference implementation targets .NET Framework, .NET, and .NET Standard 2.1.

.NET allows to develop apps that run on all common platforms available today, including Linux, iOS, Android (via Xamarin) and Windows without requiring platform-specific modifications.

One of the reference implementations inside this project has been certified for compliance through an OPC Foundation Certification Test Lab to prove its high quality. Fixes and enhancements since the certification process have been tested and verified for compliance using the latest Compliance Test Tool (CTT).

For a comprehensive list of supported OPC UA Profiles and Facets, see the dedicated documentation.

More samples based on the official Nuget packages can be found in the OPC UA .NET Samples repository. For development there is also a preview Nuget feed available. For local testing a Docker container of the Reference Server is available for preview and release builds.

Features included

Core and Libraries

Key Features and Updates in OPC UA 1.05

Breaking Changes and Heads-Up when upgrading from 1.04 to 1.05

A few features are still missing to fully comply for 1.05, but certification for V1.04 is still possible with the 1.05 release.

Thread Safety and Locking: Improved thread safety and reduced locking in secure channel operations.

Audit and Redaction: New interfaces for auditing and redacting sensitive information.

New in 1.05.378.

New in 1.05.376.

New in 1.05.375

New in 1.05.374.70

CRL Support for the X509Store on Windows

New in 1.05.373

New in 1.04.368

Samples and Nuget packages

Getting Started

All the tools you need to build .NET libraries and application come with the .NET SDK. You need the .net 10 SDK to build the project. To run applications you need one of the target .NET runtimes installed. See Get started with .NET for what you need.

How to build and run the reference samples in Visual Studio on Windows

Open the UA.slnx solution file using Visual Studio 2026. Ensure you have all target frameworks enabled, including .NET 4.8.x, .NET 8.0, 9.0, and 10.0 (LTS) but Visual Studio will prompt you to install what is missing.

Choose a project in the Solution Explorer and set it with a right click as Startup Project.

Hit F5 to build and execute the sample.

How to build and run the console samples on Windows, Linux and iOS

This section describes how to run the ConsoleReferenceServer sample application.

Please follow instructions in this article to setup the .NET 10 SDK which provides the dotnet command that allows you to build and run the samples on your platform. Once the dotnet command is available, navigate to the root folder in your local copy of the repository and execute dotnet restore 'UA.slnx'. This command calls into NuGet to restore the tree of dependencies.

Start the server

Open a command prompt.

Navigate to the folder Applications/ConsoleReferenceServer.

To run the server sample type dotnet run --project ConsoleReferenceServer.csproj -a.

The server is now running and waiting for connections.

Contributing

We strongly encourage community participation and contribution to this project. First, please fork the repository and commit your changes there. Once happy with your changes you can generate a 'pull request'.

You must agree to the contributor license agreement (CLA) before we can accept your changes. The CLA and "I AGREE" button is automatically displayed when you perform the pull request.

Remarks

Self signed certificates for the sample applications

All required application certificates for OPC UA are created at the first start of each application in a directory or OS-level certificate store and remain in use until deleted from the store. Please read Certificates for more information about certificates and stores

Local Discovery Server

By default all sample applications are configured to register with a Local Discovery Server (LDS). A reference implementation of a LDS for Windows can be downloaded here. To setup trust with the LDS the certificates need to be exchanged or registration will fail.