Opcnetapidll

// Your callback function void OnDataChanged(object subscriptionHandle, object requestHandle, ItemValueResult[] values)

The is a vital software component created by the OPC Foundation . It acts as a managed .NET wrapper, allowing modern C# and VB.NET industrial automation software to interact seamlessly with legacy OPC Classic servers.

These DLLs are technically part of the OPC Foundation redistributables.

: It provides a unified set of .NET interfaces for accessing various OPC Classic specifications. opcnetapidll

This library acts as a universal gateway for several prominent "OPC Classic" frameworks:

private Opc.IDiscovery m_discovery = new OpcCom.ServerEnumerator(); Opc.Server[] servers = m_discovery.GetAvailableServers(Specification.COM_DA_20, host, null); // Handle the array of discovered servers...

| Aspect | Details | | :--- | :--- | | | OPC .NET API Dynamic Link Library | | Main Purpose | Provides a .NET interface to interact with OPC Data Access (DA) servers for reading and writing industrial data. | | Key Dependency | Typically used alongside OpcNetApi.Com.dll , which serves as a COM interoperability wrapper. | | Core Version | A common version in use is 2.00.103.0 . | | Developer | The OPC Foundation. | | Primary Use Cases | Creating OPC DA clients/servers in .NET; building data loggers, HMI/SCADA interfaces, and MES integrations; enabling communication for .NET-based industrial software. | : It provides a unified set of

: Represent the concrete Runtime Callable Wrappers that strictly map the original C++ COM interface GUIDs into Windows system calls. Implementation Example: Reading Data in C#

OpcNetApi.dll rarely works alone. It is usually distributed alongside:

What is your application built on? Are you connecting to a local or a remote OPC server? | | Key Dependency | Typically used alongside OpcNetApi

It is primarily used to browse, read, write, and subscribe to data from OPC DA servers.

Originally designed for .NET 2.0/3.5. Newer versions (like 1.08) are required for .NET 5/6/7+.

Allowing your application to "subscribe" to tags so that it only receives updates when a value changes, rather than constantly polling the server.

If you are seeing this filename because of an error message (e.g., "opcnetapi.dll not found" or "opcnetapi.dll failed to register" ), here are the likely causes: