Once you have your objects mapped, you can invoke operations on them. The operations available depend on the type of mapper object.

For OPC Data Access (the DAClientMapper class), following methods exist for invoking operations:

• The Get method executes the “Get”, i.e. gets the values of OPC-DA properties.
• The Read method executes the “Read”, i.e. reads the data of OPC-DA items.
• The Subscribe method executes the “Subscribe”; depending on its Boolean arguments, it either subscribes to or unsubscribes from changes of OPC-DA items.
• The Write method executes the “Write”, i.e. writes data into the OPC-DA items.

For OPC Unified Architecture (the UAClientMapper class), following methods exist for invoking operations:

• The Read method executes the “Read”, i.e. reads the data of OPC-UA node attributes.
• The Subscribe method executes the “Subscribe”; depending on its Boolean arguments, it either subscribes to or unsubscribes from changes of OPC-UA node attributes (monitored items).
• The Write method executes the “Write”, i.e. writes data into the OPC-UA node attributes.

Each operation can be invoked either on all applicable mappings currently existing in the mapper, or on a specified subset of mappings. For example, the Read method on DAClientMapper has two overloads, one with no arguments (reads all item mappings that have DAItemMappingOperations.Read included in their Operations property), and one with the IEnumerable<IDAClientMapping> argument (reads just the specified mappings).

Since you typically do not have direct access to the individual mappings created for your objects (except with Type-less Mapping), you might be asking how to get access to the subset of mappings that you need. For example, you may need to perform an OPC Read on just certain mapped object, somewhere inside the whole hierarchy.

The way to obtain the set of mapping is to query the mapper itself. The Mappings property of the mapper contains an IEnumerable<> of all mappings currently maintained by the mapper. You can filter these mappings in any way you like, testing whether they fulfill your application-defined criteria, and then perform the operation just with the filtered subset.

In order to make this task easier, some extension method exist. Following methods are available for all OPC specifications:

• AbstractMappingExtension.GetTargetObject method determines the target object of the mapping. You can use it to test whether the mapping is for “your” object.
• AbstractMappingExtension.BelongsTo method determines whether a given target object belongs to this mapping, either directly, or recursively (to any of the parent mappings).

For OPC Data Access, you can use following extension methods:

• DAClientMapperExtension.GetTarget method executes the OPC-DA "Get" operation on member of given target object, directly or recursively.
• DAClientMapperExtension.ReadTarget method executes the OPC-DA "Read" operation on member of given target object, directly or recursively.
• DAClientMapperExtension.SubscribeTarget method executes the OPC-DA "Subscribe" operation on member of given target object, directly or recursively.
• DAClientMapperExtension.WriteTarget method executes the OPC-DA "Write" operation on member of given target object, directly or recursively. 

For OPC Unified Architecture, you can use the following extension methods: 

• UAMapperExtension.ReadTarget method executes the OPC-UA "Read" operation on member of given target object, directly or recursively.
• UAMapperExtension.SubscribeTarget method executes the OPC-UA "Subscribe" operation on member of given target object, directly or recursively.
• UAMapperExtension.WriteTarget method executes the OPC-UA "Write" operation on member of given target object, directly or recursively.

With each of the extension methods on the DAClientMapperExtension or UAMapperExtension, you can also specify that just members with given mapping tag, or with tags fulfilling certain condition (predicate) will be affected.

The DAClientMapper and UAClientMapper objects have a Boolean QueuedExecution property (defaults to false). When set to 'true', the operations on the mapper are executed outside the calling thread, but still in the order of arrival. This allows non-blocking operation calls on the mappers.