Throw a better error when missing conference

Currently, it throws a NullReferenceException and you have to deduce what is wrong.
dddeastanglia · Jun 6, 2019 · bdf92a9 · bdf92a9
1 parent 2a05943
commit bdf92a9
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Showing 2 changed files with 13 additions and 7 deletions.
diff --git a/DDDEastAnglia/DataAccess/ConferenceLoader.cs b/DDDEastAnglia/DataAccess/ConferenceLoader.cs
@@ -1,6 +1,7 @@
 using System;
 using DDDEastAnglia.DataAccess.SimpleData.Builders;
 using DDDEastAnglia.Domain;
+using Conference = DDDEastAnglia.DataAccess.SimpleData.Models.Conference;
 
 namespace DDDEastAnglia.DataAccess
 {
@@ -36,13 +37,23 @@ public ConferenceLoader(IConferenceRepository conferenceRepository, ConferenceBu
         public IConference LoadConference()
         {
             var dataConference = conferenceRepository.GetByEventShortName(DefaultEventName);
-            return conferenceBuilder.Build(dataConference);
+            return BuildConference(dataConference);
         }
 
         public IConference LoadConference(int sessionId)
         {
             var dataConference = conferenceRepository.ForSession(sessionId);
-            return conferenceBuilder.Build(dataConference);
+            return BuildConference(dataConference);
+        }
+
+        private IConference BuildConference(Conference conference)
+        {
+            if (conference == null)
+            {
+                throw new ArgumentNullException(nameof(conference), "Cannot find current conference");
+            }
+
+            return conferenceBuilder.Build(conference);
         }
     }
 }
diff --git a/DDDEastAnglia/DataAccess/SimpleData/Builders/ConferenceBuilder.cs b/DDDEastAnglia/DataAccess/SimpleData/Builders/ConferenceBuilder.cs
@@ -17,11 +17,6 @@ public ConferenceBuilder(ICalendarItemRepository calendarItemRepository, IBuild<
 
         public Domain.Conference Build(Conference item)
         {
-            if (item == null)
-            {
-                return null;
-            }
-
             var conference = new Domain.Conference(item.ConferenceId, item.Name, item.ShortName, item.NumberOfTimeSlots, item.NumberOfTracks, item.AnonymousSessions);
             var calendarItems = calendarItemRepository.GetAll();