(Embedded Agent) Adding components in OnRead?

[MRIIOT]

Given this example, https://github.com/TrakHound/MTConnect.NET/tree/master/examples/MTConnect.NET-Agent-Embedded, is it possible to add components to the device in the OnRead method? Or does the component hierarchy have to be built inside OnAddDevice method?

[PatrickRitchie]

Yes you should be able to add components to the device using the Device property and Agent.AddDevice() method such as below:

protected override void OnRead()
{
    // Create a Path Component
    var path = new PathComponent();

    // Add Path DataItems
    path.AddDataItem<ProgramDataItem>();

    // Add the Path Component as a child of the Controller Component
    controller.AddComponent(path);

    // Add the Controller Component to the Device
    Device.AddComponent(controller);

    // Re-Add the Device to trigger DeviceChanged event
    Agent.AddDevice(Device);
}

Let me know if this works for you or if you run into any issues.

[MRIIOT]

IDevice does not have an AddComponent method.

[PatrickRitchie]

Sorry there were a few issues with the sample code:

• You would need to cast the IDevice to the Device class in order to access the AddComponent() method
• There was an issue with adding a Device that already exists on the Agent. It didn't overwrite the existing Device. This is fixed in the v6.5.1 release I just published.

Example:

// Initial add of the Device
protected override IDevice OnAddDevice()
{
    var device = new Device();
    device.Uuid = _configuration.DeviceUuid;
    device.Id = _configuration.DeviceName;
    device.Name = _configuration.DeviceName;
    device.Description = new Description()
    {
        Manufacturer = "ACME",
        Model = "dm-500",
        SerialNumber = _configuration.SerialNumber
    };

    // Add an Availability DataItem to the Device
    device.AddDataItem<AvailabilityDataItem>();

    return device;
}

protected override void OnRead()
{
    Log(MTConnect.Logging.MTConnectLogLevel.Information, "Read PLC Data");

    // Check to see if the Component already exists
    var allComponents = Device.GetComponents();
    if (allComponents == null || !allComponents.Any(o => o.Id == "added-component"))
    {
        // Create a Path Component
        var path = new PathComponent();
        path.Id = "added-component";

        // Create a DataItem and add to Component
        var dataItem = new DateCodeDataItem();
        dataItem.Id = "added-dataitem";
        path.AddDataItem(dataItem);

        // Add the Controller Component to the Device
        ((Device)Device).AddComponent(path);

        // Re-Add the Device the Agent
        Agent.AddDevice(Device);
    }

    // Update Observation for added DataItem
    AddValueObservation("added-dataitem", DateTime.Now.ToString("o"));
}