Entity framework linq中两个计数不同的表的并集

我想将以下两个查询合并到一个列表中。怎么做

var query  = (from a in xactCtxt.XactETL_Activity_Log
                             join b in xactCtxt.XactETL_Shred_Mode on a.ShredModeID equals b.ShredModeID
                             where a.CreatedDate >= startDate && a.CreatedDate <= endDate
                             select new { a.ActivityLogID,a.ShredQueueCount,a.ShredCompletedCount,a.ShredValFailureCount,a.ShredExceptionCount, a.CreatedDate, b.ShredModeStatus })                                
                             .ToList();

                var historyCount = (from h in source.Histories
                                    where h.TransactionDate >= startDate && h.TransactionDate <= endDate
                                    select h).Count();

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有人能提出一些解决方案吗？您希望得到什么样的结果？