Saving delivery now works

Elwig/Helpers/AppDbContext.cs

@@ -122,6 +122,14 @@ namespace Elwig.Helpers {
             return c + 1;
         }
 
+        public async Task<int> NextDId(int year) {
+            return await Deliveries.Where(d => d.Year == year).Select(d => d.DId).MaxAsync() + 1;
+        }
+
+        public async Task<int> NextDPNr(int year, int did) {
+            return await DeliveryParts.Where(p => p.Year == year && p.DId == did).Select(d => d.DPNr).MaxAsync() + 1;
+        }
+
         public async Task<WineQualLevel> GetWineQualityLevel(double kmw) {
             return await WineQualityLevels
                 .Where(q => !q.IsPredicate && (q.MinKmw == null || q.MinKmw <= kmw))