ProcessHost is a read-only property of the IMessageSendNames interface that returns the message parameter name expected by the MessageLog2.SendLogMessage method for specifying the fully qualified domain name (FQDN) of the machine that is sending the message.
The MessageLog2.SendLogMessage method will automatically add the ProcessHost to any log message sent to a PI server's Message log (remote messages). When sending messages to the local log it is assumed the process host is the same as the host of the PI Message subsystem and this parameter is not logged automatically but may be sent by an application.
The object placeholder is an object expression that evaluates to a IMessageSendNames interface.
The IMessageSendNames interface can be obtained directly from the MessageLog2.MessageSendNames property or by using QueryInterface (assignment, in VB, casting in .Net) on a MessageLog or MessageLog2 object.
When adding to the NamedValues collection, the IMessageSendNames interface acts with Intellisense to show the available parameter options and ensures only names that are supported are used.