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.
             
            
 Declaration Syntax
 Declaration Syntax| C# | 
public long ExternalInitiatedEventId { get; set; }