CalendarEvent: Don't set DURATION resp. DTEND from each other. Only calculate the duration on the fly when needed. This way we don't overwrite the information, which of both was originally set and can adjust calculations accordingly (in the future). See #574.

Author: minichma

Ical.Net.Tests/DeserializationTests.cs

@@ -1,4 +1,4 @@
-using Ical.Net.CalendarComponents;
+using Ical.Net.CalendarComponents;
 using Ical.Net.DataTypes;
 using Ical.Net.Serialization;
 using Ical.Net.Serialization.DataTypes;
@@ -505,5 +505,25 @@ public void Property1()
                 Assert.AreEqual("2." + i, props[i].Value);
             }
         }
+
+
+        [Test]
+        [TestCase(true)]
+        [TestCase(false)]
+        public void KeepApartDtEndAndDuration_Tests(bool useDtEnd)
+        {
+            var calStr = $@"BEGIN:VCALENDAR
+BEGIN:VEVENT
+DTSTART:20070406T230000Z
+{(useDtEnd ? "DTEND:20070407T010000Z" : "DURATION:PT1H")}
+END:VEVENT
+END:VCALENDAR
+";
+
+            var calendar = Calendar.Load(calStr);
+
+            Assert.AreEqual(useDtEnd, calendar.Events.Single().DtEnd != null);
+            Assert.AreEqual(!useDtEnd, calendar.Events.Single().Duration != default);
+        }
     }
 }

Ical.Net.Tests/SymmetricSerializationTests.cs

@@ -19,7 +19,17 @@ public class SymmetricSerializationTests
         private static readonly DateTime _later = _nowTime.AddHours(1);
         private static CalendarSerializer GetNewSerializer() => new CalendarSerializer();
         private static string SerializeToString(Calendar c) => GetNewSerializer().SerializeToString(c);
-        private static CalendarEvent GetSimpleEvent() => new CalendarEvent {DtStart = new CalDateTime(_nowTime), DtEnd = new CalDateTime(_later)};
+        private static CalendarEvent GetSimpleEvent(bool useDtEnd = true)
+        {
+            var evt = new CalendarEvent { DtStart = new CalDateTime(_nowTime) };
+            if (useDtEnd)
+                evt.DtEnd = new CalDateTime(_later);
+            else
+                evt.Duration = _later - _nowTime;
+
+            return evt;
+        }
+
         private static Calendar UnserializeCalendar(string s) => Calendar.Load(s);
 
         [Test, TestCaseSource(nameof(Event_TestCases))]
@@ -38,24 +48,33 @@ public void Event_Tests(Calendar iCalendar)
         }
 
         public static IEnumerable<ITestCaseData> Event_TestCases()
+        {
+            return Event_TestCasesInt(true).Concat(Event_TestCasesInt(false));
+        }
+
+        private static IEnumerable<ITestCaseData> Event_TestCasesInt(bool useDtEnd)
         {
             var rrule = new RecurrencePattern(FrequencyType.Daily, 1) { Count = 5 };
             var e = new CalendarEvent
             {
                 DtStart = new CalDateTime(_nowTime),
-                DtEnd = new CalDateTime(_later),
                 RecurrenceRules = new List<RecurrencePattern> { rrule },
             };
 
+            if (useDtEnd)
+                e.DtEnd = new CalDateTime(_later);
+            else
+                e.Duration = _later - _nowTime;
+                    
             var calendar = new Calendar();
             calendar.Events.Add(e);
-            yield return new TestCaseData(calendar).SetName("readme.md example");
+            yield return new TestCaseData(calendar).SetName($"readme.md example with {(useDtEnd ? "DTEND" : "DURATION")}");
 
-            e = GetSimpleEvent();
+            e = GetSimpleEvent(useDtEnd);
             e.Description = "This is an event description that is really rather long. Hopefully the line breaks work now, and it's serialized properly.";
             calendar = new Calendar();
             calendar.Events.Add(e);
-            yield return new TestCaseData(calendar).SetName("Description serialization isn't working properly. Issue #60");
+            yield return new TestCaseData(calendar).SetName($"Description serialization isn't working properly. Issue #60 {(useDtEnd ? "DTEND" : "DURATION")}");
         }
 
         [Test]

Ical.Net/CalendarComponents/CalendarEvent.cs

@@ -26,27 +26,6 @@ public class CalendarEvent : RecurringComponent, IAlarmContainer, IComparable<Ca
     {
         internal const string ComponentName = "VEVENT";
 
-        /// <summary>
-        /// The start date/time of the event.
-        /// <note>
-        /// If the duration has not been set, but
-        /// the start/end time of the event is available,
-        /// the duration is automatically determined.
-        /// Likewise, if the end date/time has not been
-        /// set, but a start and duration are available,
-        /// the end date/time will be extrapolated.
-        /// </note>
-        /// </summary>
-        public override IDateTime DtStart
-        {
-            get => base.DtStart;
-            set
-            {
-                base.DtStart = value;
-                ExtrapolateTimes(2);
-            }
-        }
-
         /// <summary>
         /// The end date/time of the event.
         /// <note>
@@ -66,7 +45,6 @@ public virtual IDateTime DtEnd
                 if (!Equals(DtEnd, value))
                 {
                     Properties.Set("DTEND", value);
-                    ExtrapolateTimes(0);
                 }
             }
         }
@@ -100,11 +78,24 @@ public virtual TimeSpan Duration
                 if (!Equals(Duration, value))
                 {
                     Properties.Set("DURATION", value);
-                    ExtrapolateTimes(1);
                 }
             }
         }
 
+        /// <summary>
+        /// Calculates and returns the effective duration of this event.
+        /// </summary>
+        /// <remarks>
+        /// If the 'DURATION' property iis set, this method will return it.
+        /// Otherwise, if DTSTART and DTEND are set, it will calculate the duration from those.
+        /// Otherwise it will return `default(TimeSpan)`.
+        /// </remarks>
+        /// <returns>The effective duration of this event.</returns>
+        public virtual TimeSpan GetEffectiveDuration()
+            => (Properties.ContainsKey("DURATION")) ? Duration
+            : ((DtEnd != null) && (DtStart != null)) ? DtEnd.Subtract(DtStart)
+            : default(TimeSpan);
+
         /// <summary>
         /// An alias to the DtEnd field (i.e. end date/time).
         /// </summary>
@@ -257,26 +248,6 @@ protected override void OnDeserializing(StreamingContext context)
         protected override void OnDeserialized(StreamingContext context)
         {
             base.OnDeserialized(context);
-
-            ExtrapolateTimes(-1);
-        }
-
-        private void ExtrapolateTimes(int source)
-        {
-            /*
-			 * Source values, a fix introduced to prevent stack overflow exceptions from occuring.
-			 *   -1 = Anybody, stack overflow could maybe still occur in this case?
-			 *    0 = End
-			 *	  1 = Duration
-			 */
-            if (DtEnd == null && DtStart != null && Duration != default(TimeSpan) && source != 0)
-            {
-                DtEnd = DtStart.Add(Duration);
-            }
-            else if (Duration == default(TimeSpan) && DtStart != null && DtEnd != null && source != 1)
-            {
-                Duration = DtEnd.Subtract(DtStart);
-            }
         }
 
         protected bool Equals(CalendarEvent other)
@@ -289,6 +260,7 @@ protected bool Equals(CalendarEvent other)
                 && string.Equals(Summary, other.Summary, StringComparison.OrdinalIgnoreCase)
                 && string.Equals(Description, other.Description, StringComparison.OrdinalIgnoreCase)
                 && Equals(DtEnd, other.DtEnd)
+                && Equals(Duration, other.Duration)
                 && string.Equals(Location, other.Location, StringComparison.OrdinalIgnoreCase)
                 && resourcesSet.SetEquals(other.Resources)
                 && string.Equals(Status, other.Status, StringComparison.Ordinal)
@@ -348,6 +320,7 @@ public override int GetHashCode()
                 var hashCode = DtStart?.GetHashCode() ?? 0;
                 hashCode = (hashCode * 397) ^ (Summary?.GetHashCode() ?? 0);
                 hashCode = (hashCode * 397) ^ (Description?.GetHashCode() ?? 0);
+                hashCode = (hashCode * 397) ^ Duration.GetHashCode();
                 hashCode = (hashCode * 397) ^ (DtEnd?.GetHashCode() ?? 0);
                 hashCode = (hashCode * 397) ^ (Location?.GetHashCode() ?? 0);
                 hashCode = (hashCode * 397) ^ Status?.GetHashCode() ?? 0;

Ical.Net/Evaluation/EventEvaluator.cs

@@ -40,19 +40,19 @@ public override HashSet<Period> Evaluate(IDateTime referenceTime, DateTime perio
 
             foreach (var period in Periods)
             {
-                period.Duration = CalendarEvent.Duration;
+                period.Duration = CalendarEvent.GetEffectiveDuration();
                 period.EndTime = period.Duration == default
                     ? period.StartTime
-                    : period.StartTime.Add(CalendarEvent.Duration);
+                    : period.StartTime.Add(CalendarEvent.GetEffectiveDuration());
             }
 
             // Ensure each period has a duration
             foreach (var period in Periods.Where(p => p.EndTime == null))
             {
-                period.Duration = CalendarEvent.Duration;
+                period.Duration = CalendarEvent.GetEffectiveDuration();
                 period.EndTime = period.Duration == default
                     ? period.StartTime
-                    : period.StartTime.Add(CalendarEvent.Duration);
+                    : period.StartTime.Add(CalendarEvent.GetEffectiveDuration());
             }
 
             return Periods;