Quick Start

Connect and Read a Value

The simplest use case: connect to an OPC UA server, read a node value, and disconnect.

using OpcSharp.Client;
using OpcSharp.Types;

var client = new OpcSharpClientBuilder()
    .WithEndpoint("opc.tcp://localhost:4840")
    .Build();

await client.ConnectAsync();

// Read the Server.ServerStatus.CurrentTime node
var results = await client.ReadAsync(new[]
{
    new ReadValueId
    {
        NodeId = new NodeId(0, 2258),
        AttributeId = AttributeIds.Value
    }
});

Console.WriteLine($"Server time: {results[0].Value}");
await client.DisconnectAsync();

Write a Value

var statusCodes = await client.WriteAsync(new[]
{
    new WriteValue
    {
        NodeId = new NodeId(2, "MyVariable"),
        AttributeId = AttributeIds.Value,
        Value = new DataValue(new Variant(42))
    }
});

Browse the Address Space

var browseResults = await client.BrowseAsync(new[]
{
    new BrowseDescription
    {
        NodeId = ObjectIds.ObjectsFolder,
        BrowseDirection = BrowseDirection.Forward,
        ReferenceTypeId = ReferenceTypeIds.HierarchicalReferences,
        IncludeSubtypes = true,
        ResultMask = (uint)BrowseResultMask.All
    }
});

foreach (var reference in browseResults[0].References)
{
    Console.WriteLine($"{reference.DisplayName} ({reference.NodeId})");
}

Subscribe to Data Changes

var subscription = await client.CreateSubscriptionAsync(
    publishingInterval: 1000);

var monitoredItems = await client.CreateMonitoredItemsAsync(
    subscription.SubscriptionId,
    new[]
    {
        new MonitoredItemCreateRequest
        {
            ItemToMonitor = new ReadValueId
            {
                NodeId = new NodeId(0, 2258),
                AttributeId = AttributeIds.Value
            },
            MonitoringMode = MonitoringMode.Reporting,
            RequestedParameters = new MonitoringParameters
            {
                SamplingInterval = 500,
                QueueSize = 10
            }
        }
    });

client.DataChanged += (sender, args) =>
{
    Console.WriteLine($"Value changed: {args.Value}");
};

// Keep the application running to receive notifications
await Task.Delay(Timeout.Infinite);

Complete Getting Started Sample

A standalone sample project is available at samples/GettingStarted that uses OpcSharp via NuGet packages (not project references) — exactly how end users would consume the SDK.

Create the project

mkdir MyOpcUaApp && cd MyOpcUaApp
dotnet new console
dotnet add package OpcSharp.Client

Full example

The complete source is at samples/GettingStarted/Program.cs. It connects to an OPC UA server, reads values, browses the address space, discovers endpoints, subscribes to data changes for 5 seconds, and cleans up.

Run it

# Clone and run
git clone https://github.com/patdhlk/OpcSharp.git
cd OpcSharp

# Start the test OPC UA server
docker compose -f docker/docker-compose.yml up -d

# Run the sample (uses NuGet packages, not project references)
dotnet run --project samples/GettingStarted

Using Dependency Injection

services.AddOpcSharpClient("MyClient", options =>
{
    options.EndpointUrl = "opc.tcp://localhost:4840";
    options.Security.PolicyUri = SecurityPolicyUris.None;
});

// Inject IOpcSharpClientFactory and create a named client
public class MyService(IOpcSharpClientFactory clientFactory)
{
    public async Task ReadAsync()
    {
        var client = clientFactory.CreateClient("MyClient");
        await client.ConnectAsync();
        // ...
    }
}

Installation Architecture