This property returns a reference to an IMessageSendNames interface. The ISendFilterNames interface provides properties that return strings which are the official names of the supported message properties that can be sent with messages that have been added to messaging for PI server versions 3.4.380 and beyond. The purpose of the interface is to allow the user to easily build the collection of additional message properties for calling the SendLogMessage method of the MessageLog2 object. The interface shows which fields are possible and provides the proper name to be used when constructing the NamedValues collection of additional message properties. Even though the additional message properties were added to the server message subsystem with version 3.4.380, the SendLogMessage method can be used with older servers and these same properties can be passed by the caller. In that case the PI-SDK will detect the target message subsystem version and automatically add the new unsupported properties to the text of the logged message.
The object placeholder is an object expression that evaluates to a MessageLog2 object.
It is also possible to obtain the IMessageFilterNames interface from either a MessageLog2 or MessageLog object by using the COM method QueryInterface. In Visual Basic this can be accomplished using the set command to assign the object to a variable of the interface type. Similar techniques are available in .Net.
The interface works in conjunction with Intellisense displaying available properties in a dropdown as the code is written.