dOPC Client Toolkit
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dOPCAE.TdOPCEvent.ChangeMask

ChangeMask indicates what properties of the condition have changed and forced the server to send the event notification.

property ChangeMask: integer;
__property int ChangeMask;
Value
Description
opc_Change_Active_State
the condition's active state has changed
opc_Change_Ack_State
the condition's acknowledgment state has changed
opc_Change_Enable_State
the condition's enabled state has changed
opc_Change_Quality
the condition's quality has changed
opc_Change_Severity
the severity level has changed
opc_Change_Subcondition
the condition has transitioned into a new sub-condition
opc_Change_Message
the event message has changed (compared to prior event notifications related to this condition)
opc_Change_Attribute
one or more event attributes have changed (compared to prior event notifications related to this condition)

If the event notification is the result of a refresh, these bits have to be ignored. For a "new event", opc_Change_Active_State is the only bit which will always be set. Other values are server-specific. (A "new event" is any event resulting from the related condition leaving the Inactive and Acknowledged state.)

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