The id of the SignalExternalWorkflowExecutionInitiated event corresponding to the SignalExternalWorkflow decision to signal this workflow execution.The source event with this Id can be found in the history of the source workflow execution. This information can be useful for diagnosing problems by tracing back the chain of events leading up to this event. This field is set only if the signal was initiated by another workflow execution.

public long ExternalInitiatedEventId { get; set; }