Enhance RecurrencePatternSerializer

Ical.Net.Tests/RecurrenceTests.cs

@@ -9,7 +9,6 @@
 using System.Globalization;
 using System.IO;
 using System.Linq;
-using System.Reflection;
 using System.Text.RegularExpressions;
 using Ical.Net.CalendarComponents;
 using Ical.Net.DataTypes;
@@ -1233,8 +1232,8 @@
         var rpe1 = new RecurrencePatternEvaluator(new RecurrencePattern("FREQ=YEARLY;WKST=MO;BYDAY=MO;BYWEEKNO=1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49,51,53"));
         var rpe2 = new RecurrencePatternEvaluator(new RecurrencePattern("FREQ=YEARLY;WKST=MO;BYDAY=MO;BYWEEKNO=53,51,49,47,45,43,41,39,37,35,33,31,29,27,25,23,21,19,17,15,13,11,9,7,5,3,1"));
 
         var recurringPeriods1 = rpe1.Evaluate(new CalDateTime(start), start, end, default).ToList();
         var recurringPeriods2 = rpe2.Evaluate(new CalDateTime(start), start, end, default).ToList();
 
         Assert.That(recurringPeriods2, Has.Count.EqualTo(recurringPeriods1.Count));
     }
@@ -2628,7 +2627,7 @@
         var end = new CalDateTime(2019, 12, 31);
         var rpe = new RecurrencePatternEvaluator(new RecurrencePattern("FREQ=WEEKLY;BYDAY=MO;BYWEEKNO=2"));
 
         var recurringPeriods = rpe.Evaluate(start, start, end, default).ToList();
 
         Assert.That(recurringPeriods, Has.Count.EqualTo(1));
         Assert.That(recurringPeriods.First().StartTime, Is.EqualTo(new CalDateTime(2019, 1, 7)));
@@ -2644,7 +2643,7 @@
         var end = new CalDateTime(2020, 12, 31);
         var rpe = new RecurrencePatternEvaluator(new RecurrencePattern("FREQ=WEEKLY;BYDAY=MO;BYMONTH=1"));
 
         var recurringPeriods = rpe.Evaluate(start, start, end, default).OrderBy(x => x).ToList();
 
         Assert.That(recurringPeriods, Has.Count.EqualTo(4));
         Assert.Multiple(() =>
@@ -3944,4 +3943,35 @@
 
         Assert.That(() => cal.GetOccurrences(options: options).ToList(), constraint);
     }
+
+    [TestCase("FREQ=DAILY;INTERVAL=2;UNTIL=20250430T000000Z")]
+    [TestCase("UNTIL=20250430T000000Z;FREQ=DAILY;INTERVAL=2")]
+    [TestCase("INTERVAL=2;FREQ=DAILY;UNTIL=20250430T000000Z")]
+    [TestCase("INTERVAL=2;UNTIL=20250430T000000Z;FREQ=DAILY")]
+    public void Recurrence_RRULE_Properties_ShouldBeDeserialized_In_Any_Order(string rRule)
+    {
+        var serializer = new RecurrencePatternSerializer();
+        var recurrencePattern = serializer.Deserialize(new StringReader(rRule)) as RecurrencePattern;
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(recurrencePattern, Is.Not.Null);
+            Assert.That(recurrencePattern?.Until, Is.Not.Null);
+            Assert.That(recurrencePattern?.Until, Is.EqualTo(new CalDateTime(2025, 4, 30, 0, 0, 0, CalDateTime.UtcTzId)));
+            Assert.That(recurrencePattern?.Frequency, Is.EqualTo(FrequencyType.Daily));
+            Assert.That(recurrencePattern?.Interval, Is.EqualTo(2));
+        });
+    }
+
+    [Test]
+    public void Disallowed_Recurrence_RangeChecks_Should_Throw()
+    {
+        var serializer = new RecurrencePatternSerializer();
+        Assert.Multiple(() =>
+        {
+            Assert.That(() => serializer.CheckMutuallyExclusive("a", "b", 1, CalDateTime.Now), Throws.TypeOf<ArgumentOutOfRangeException>());
+            Assert.That(() => serializer.CheckRange("a", 0, 1, 2, false), Throws.TypeOf<ArgumentOutOfRangeException>());
+            Assert.That(() => serializer.CheckRange("a", (int?) 0, 1, 2, false), Throws.TypeOf<ArgumentOutOfRangeException>());
+        });
+    }
 }

Ical.Net/DataTypes/RecurrencePattern.cs

@@ -81,6 +81,10 @@ public int Interval
     /// </summary>
     public List<int> ByMonth { get; set; } = new List<int>();
 
+    /// <summary>
+    /// Specify the n-th occurrence within the set of occurrences specified by the RRULE.
+    /// It is typically used in conjunction with other rule parts like BYDAY, BYMONTHDAY, etc.
+    /// </summary>
     public List<int> BySetPosition { get; set; } = new List<int>();
 
     public DayOfWeek FirstDayOfWeek { get; set; } = DayOfWeek.Monday;