How to get Stimulsoft report result length - c# - Asp.net Web Forms

I need to get final report's file size to log as the history of user's downloads. Here is the code to prepare the report:

Stimulsoft.Report.StiReport report = new Stimulsoft.Report.StiReport();
report.Dictionary.DataStore.Clear();
report.Load(Server.MapPath(@"~\ReportFiles\ReportFoodServe.mrt"));
DataSet dsa = new DataSet();
dsa.Tables.Add((_Dt_Reserve).Copy());        
dsa.Tables[0].TableName = "Details";        
report.RegData(dsa);
report.Dictionary.Synchronize();
report.Compile();                
report.Render(); 
StPrint.ResetReport();
StPrint.Report = report;

long resultLength =  report.??? // Length of report   

//Log here:
LogFileDownload("LeaveReportFileName", resultLength);