/// <summary>
/// Is used to one-time read value.
/// Callback is invoked when valueStatusTimestamp.ValueStatusCode != StatusCodes.Unknown
/// </summary>
public ReadOnceValueSubscription(IDataAccessProvider dataProvider, string elementId, Action <ValueStatusTimestamp>?setValueAction)
{
_dataProvider = dataProvider;
_setValueAction = setValueAction;
_dataProvider.AddItem(elementId, this);
}
/// <summary>
/// Is used to subscribe for value updating and to write values.
/// valueUpdated(oldValue, newValue) is invoked when Value property Updated. Initial Value property is new ValueStatusTimestamp(), Any(null) and Unknown status.
/// </summary>
public ValueSubscription(IDataAccessProvider dataAccessProvider, string elementId, Action <ValueStatusTimestamp, ValueStatusTimestamp>?valueUpdated = null)
{
DataAccessProvider = dataAccessProvider;
ElementId = elementId;
_valueUpdated = valueUpdated;
DataAccessProvider.AddItem(ElementId, this);
}
