OpcLabs.EasyOpc.DataAccess.Generic Namespace

This namespace contains classes for OPC Data Access that use generics.

Classes

	Class	Description
	DAItemValueArguments<TValue>	Holds an OPC server and item descriptor, and a typed data value, as arguments to some operation.
	DAItemVtqArguments<T>	Holds an OPC server and item descriptor, and a typed value/timestamp/quality (OpcLabs.EasyOpc.DataAccess.DAVtq), as arguments to some operation.
	DAVtq<TValue>	Holds typed data value, timestamp and quality, abbreviated sometimes as VTQ. This is a common combination in OPC, e.g. returned when an OPC item is read.
	DAVtqResult<TValue>	Holds result of an operation in form of a typed DAVtq<TValue> (value, timestamp, and quality).
	EasyDAItemChangedEventArgs<TValue>	Provides typed data for an event raised for every significant change in a subscribed OPC item.
	EasyDAItemSubscriptionArguments<T>	Holds an OPC server and item descriptor, and OPC group parameters, and possibly a typed callback method, as arguments to subscription operation.

Delegates

	Delegate	Description
	EasyDAItemChangedEventHandler<TValue>	Represents the method that will handle an event raised for every significant change in a subscribed OPC item.

Remarks

Following generic types are available for use with OPC Data Access and OPC XML-DA:

DAVtq<T>: Holds typed data value (of type T), timestamp, and quality.
DAVtqResult<T>: Holds result of an operation in form of a typed DAVtq<T> (value, timestamp, quality).
DAItemValueArguments<T>: Arguments for an operation on an OPC item. Carries a value of type T.
DAItemVtqArguments<T>: Arguments for an operation on an OPC item. Carries a DAVtq<T> object.
EasyDAItemSubscriptionArguments<T>: Arguments for subscribing to an OPC item of type T.
EasyDAItemChangedEventArgs<T>: Data of an event or callback for a significant change in OPC item of type T.

These types are used with generic access extensions for OPC items (see Generic Access) and with generic access extensions for OPC properties (see Generic Access). They are also use with the Live Mapping Model.

For example, you can call the EasyDAClient.ReadItem<T> extension method with a given type T, and receive back a DAVtq<T> object with a TypedValue already properly typed as T.

Noted that if the untyped property on the base (non-generic) type has a name like XXXX, the corresponding typed property on the generic type has a name like TypedXXXX. For example, for an untyped property DAVtqResult.Vtq, there is a corresponding typed property DAVtqResult<T>.TypedVtq.

Reference

OpcLabs.EasyOpcClassicCore Assembly

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