метод получения доступного интервала наработки подсистем

AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs

@@ -185,6 +185,21 @@ namespace AsbCloudInfrastructure.Services.Subsystems
 
         }
 
+        private (DateTimeOffset, DateTimeOffset) GetDateRangeOperationTime(int idSubsystem)
+        {
+            var dateRange = db.SubsystemOperationTimes
+                .Where(o => o.Id == idSubsystem)
+                .GroupBy(o => o.IdSubsystem)
+                .Select(g => new
+                {
+                    DateFirst = g.Min(o => o.DateStart),
+                    DateLast = g.Max(o => o.DateEnd)
+                })
+                .FirstOrDefault();           
+            (DateTimeOffset dateFirst, DateTimeOffset dateLast) result = (dateRange.DateFirst, dateRange.DateLast);
+            return result;
+        }
+
         private IQueryable<SubsystemOperationTime>? BuildQuery(SubsystemOperationTimeRequest request)
         {
             var well = wellService.GetOrDefault(request.IdWell);