Class RecurrenceEvaluator

Evaluates a RecurrenceRule (RFC 5545 §3.3.10) to generate occurrence date-times. Given a rule and a start date-time (DTSTART), the evaluator produces the ordered set of date-times that satisfy the rule, bounded by COUNT, UNTIL, or an explicit range.

Inheritance

object

RecurrenceEvaluator

Inherited Members

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

Namespace: DRIT.Mail.Rfc.ICal

Assembly: DRIT.Mail.dll

Syntax

public static class RecurrenceEvaluator

Remarks

The evaluation follows the algorithm described in RFC 5545 §3.3.10. For each interval period (determined by FREQ and INTERVAL), candidate date-times are generated by applying the BY* rules in the order defined by the specification:

1. BYMONTH
2. BYWEEKNO
3. BYYEARDAY
4. BYMONTHDAY
5. BYDAY
6. BYHOUR
7. BYMINUTE
8. BYSECOND

After expansion, BYSETPOS selects specific positions within the period's candidate set. The result is filtered by UNTIL and limited by COUNT.

The first occurrence is always DTSTART itself, provided it falls within the bounds. Per RFC 5545 §3.3.10, the recurrence set is generated by considering the period containing DTSTART as the first period, even if DTSTART does not strictly match the BY* rules (DTSTART is always included as the first occurrence).

Fields

DefaultMaxOccurrences

The default maximum number of occurrences generated when neither COUNT, UNTIL, nor an explicit range bound the result. This guards against unbounded recurrence rules (e.g. FREQ=DAILY with no end).

Declaration

public const int DefaultMaxOccurrences = 1000

Field Value

Type	Description
int

Remarks

The evaluation follows the algorithm described in RFC 5545 §3.3.10. For each interval period (determined by FREQ and INTERVAL), candidate date-times are generated by applying the BY* rules in the order defined by the specification:

1. BYMONTH
2. BYWEEKNO
3. BYYEARDAY
4. BYMONTHDAY
5. BYDAY
6. BYHOUR
7. BYMINUTE
8. BYSECOND

After expansion, BYSETPOS selects specific positions within the period's candidate set. The result is filtered by UNTIL and limited by COUNT.

The first occurrence is always DTSTART itself, provided it falls within the bounds. Per RFC 5545 §3.3.10, the recurrence set is generated by considering the period containing DTSTART as the first period, even if DTSTART does not strictly match the BY* rules (DTSTART is always included as the first occurrence).

Methods

Evaluate(RecurrenceRule, ICalDateTime)

Evaluates the specified recurrence rule starting from start, returning all occurrences. The result is bounded by COUNT or UNTIL if present in the rule; otherwise it is bounded by DefaultMaxOccurrences.

Declaration

public static IReadOnlyList<ICalDateTime> Evaluate(RecurrenceRule rule, ICalDateTime start)

Parameters

Type	Name	Description
RecurrenceRule	rule	The recurrence rule to evaluate. Must not be null.
ICalDateTime	start	The start date-time (DTSTART). Must not be null.

Returns

Type	Description
IReadOnlyList<ICalDateTime>	An ordered list of occurrence date-times, starting with start.

Remarks

The evaluation follows the algorithm described in RFC 5545 §3.3.10. For each interval period (determined by FREQ and INTERVAL), candidate date-times are generated by applying the BY* rules in the order defined by the specification:

1. BYMONTH
2. BYWEEKNO
3. BYYEARDAY
4. BYMONTHDAY
5. BYDAY
6. BYHOUR
7. BYMINUTE
8. BYSECOND

After expansion, BYSETPOS selects specific positions within the period's candidate set. The result is filtered by UNTIL and limited by COUNT.

The first occurrence is always DTSTART itself, provided it falls within the bounds. Per RFC 5545 §3.3.10, the recurrence set is generated by considering the period containing DTSTART as the first period, even if DTSTART does not strictly match the BY* rules (DTSTART is always included as the first occurrence).

Evaluate(RecurrenceRule, ICalDateTime, ICalDateTime?, ICalDateTime?, int)

Evaluates the specified recurrence rule starting from start, returning all occurrences that fall within the range [rangeStart, rangeEnd]. The result is also bounded by COUNT or UNTIL if present in the rule.

Declaration

public static IReadOnlyList<ICalDateTime> Evaluate(RecurrenceRule rule, ICalDateTime start, ICalDateTime? rangeStart, ICalDateTime? rangeEnd, int maxOccurrences)

Parameters

Type	Name	Description
RecurrenceRule	rule	Specifies the rule value.
ICalDateTime	start	Specifies the start value.
ICalDateTime	rangeStart	The inclusive lower bound of the range, or null for no lower bound. Occurrences before this bound are still counted toward COUNT but are not returned.
ICalDateTime	rangeEnd	The inclusive upper bound of the range, or null for no upper bound (in which case maxOccurrences bounds the result).
int	maxOccurrences	The maximum number of occurrences to generate, regardless of other bounds. This guards against unbounded rules.

Returns

Type	Description
IReadOnlyList<ICalDateTime>	An ordered list of occurrence date-times within the specified range, starting with start if it falls within the range.

Remarks

The evaluation follows the algorithm described in RFC 5545 §3.3.10. For each interval period (determined by FREQ and INTERVAL), candidate date-times are generated by applying the BY* rules in the order defined by the specification:

1. BYMONTH
2. BYWEEKNO
3. BYYEARDAY
4. BYMONTHDAY
5. BYDAY
6. BYHOUR
7. BYMINUTE
8. BYSECOND

After expansion, BYSETPOS selects specific positions within the period's candidate set. The result is filtered by UNTIL and limited by COUNT.

The first occurrence is always DTSTART itself, provided it falls within the bounds. Per RFC 5545 §3.3.10, the recurrence set is generated by considering the period containing DTSTART as the first period, even if DTSTART does not strictly match the BY* rules (DTSTART is always included as the first occurrence).