Convert System.DayOfWeek into Microsoft.Office.Interop.Outlook.OlDaysOfWeek

Question

Is there a possibility to directly convert a value of System.DayOfWeek into a value of Microsoft.Office.Interop.Outlook.OlDaysOfWeek. Something like:

var day = DayOfWeek.Friday;
OlDaysOfWeek days = ConvertToDaysOfWeek(day);

There's no direct conversion, but you can write one, probably using a `switch` statement. — DavidG, Apr 16 '19 at 10:54
From your links it looks like the integer values behind the enums are different. I would write my own conversion method. — Uwe Keim, Apr 16 '19 at 10:55

smolchanovsky · Answer 1 · 2019-04-16T11:05:43.423

2

You can try this:

var olDay = (OlDaysOfWeek) Enum.Parse(typeof(OlDaysOfWeek), $"ol{systemDay}");

edited Apr 16 '19 at 11:05

answered Apr 16 '19 at 11:00

smolchanovsky

1,775
2
15
29

Clever. Bonus points if you wrap it in extensions methods for converting in both directions. – Bradley Uffner Apr 16 '19 at 11:01
Bonus points if you can do this without string manipulation which is very slow. – DavidG Apr 16 '19 at 11:02
@DavidG I thought the same thing at first too, but it's already going through a com interop layer. I doubt the string manipulation is the bottle-neck. – Bradley Uffner Apr 16 '19 at 11:03
Extra note: You don't need to call `ToString()` on objects embedded in a string interpolation. It's implicit. – Bradley Uffner Apr 16 '19 at 11:05
@DavidG conversion by value is less safe – smolchanovsky Apr 16 '19 at 11:08

score 2 · Answer 2 · answered Apr 16 '19 at 11:05

2

To do this without using string manipulation, here's an option:

public OlDaysOfWeek ConvertToDaysOfWeek(DayOfWeek day)
{
    return (OlDaysOfWeek)Math.Pow(2, (int)day); 
}

answered Apr 16 '19 at 11:05

DavidG

113,891
12
217
223

This is the most terse form of conversion, good call o `Math.Pow` – Matthew Abbott Apr 16 '19 at 11:15

Matthew Abbott · Answer 3 · 2019-04-16T11:13:15.087

A simple switch statement would probably be most performant:

public OlDaysOfWeek ConvertToDaysOfWeek(DayOfWeek day)
{
  switch (day)
  {
    case DayOfWeek.Monday: return OlDaysOfWeek.olMonday;
    case DayOfWeek.Tuesday: return OlDaysOfWeek.olTuesday;
    case DayOfWeek.Wednesday: return OlDaysOfWeek.olWednesday;
    case DayOfWeek.Thursday: return OlDaysOfWeek.olThursday;
    case DayOfWeek.Friday: return OlDaysOfWeek.olFriday;
    case DayOfWeek.Saturday: return OlDaysOfWeek.olSaturday;
    case DayOfWeek.Sunday: return OlDaysOfWeek.olSunday;
    default: throw new ArgumentOutOfRangeException("What day is this?", "day");
  }
}

Alternatively, you could probably parse the value and return the mapped value based on the enum value name.

public OlDaysOfWeek ConvertToDaysOfWeek(DayOfWeek day)
{
  return (OlDaysOfWeek) Enum.Parse(typeof(OlDaysOfWeek), "ol" + day.ToString());
}

The OlDaysOfWeek enum utilises a power-of-2 sequence, which is typically used when combining values as bitwise flags. DaysOfWeek has a simple linear sequence reflected as 0-6 - this is why you can't compare using the backing int value

Not quite right in your last paragraph, both enums use Sunday as the first day. — DavidG, Apr 16 '19 at 11:06

scher · Answer 4 · 2019-04-16T11:17:24.047

1

Finally I found the following solution. Thanks for the hints.

public static OlDaysOfWeek AsDaysOfWeek(this DayOfWeek dayOfWeek)
{
    return (OlDaysOfWeek)(1 << (int)dayOfWeek);
}

To be used like this:

var day = DayOfWeek.Friday;
OlDaysOfWeek days = day.AsDaysOfWeek();

Additionally these are the unit tests in NUnit for the method:

[TestCase(DayOfWeek.Monday, OlDaysOfWeek.olMonday)]
[TestCase(DayOfWeek.Tuesday, OlDaysOfWeek.olTuesday)]
[TestCase(DayOfWeek.Wednesday, OlDaysOfWeek.olWednesday)]
[TestCase(DayOfWeek.Thursday, OlDaysOfWeek.olThursday)]
[TestCase(DayOfWeek.Friday, OlDaysOfWeek.olFriday)]
[TestCase(DayOfWeek.Saturday, OlDaysOfWeek.olSaturday)]
[TestCase(DayOfWeek.Sunday, OlDaysOfWeek.olSunday)]
public void AsDaysOfWeek(DayOfWeek dayOfWeek, OlDaysOfWeek expectedResult)
{
    var result = dayOfWeek.AsDaysOfWeek();

    Assert.That(result, Is.EqualTo(expectedResult));
}

edited Apr 16 '19 at 11:17

answered Apr 16 '19 at 11:08

scher

1,813
2
18
39

Did you find this answer online? – DavidG Apr 16 '19 at 11:14
Note that you will have problems if any of the enumeration options change value. – smolchanovsky Apr 16 '19 at 11:16
"Additionally these are the unit tests" - you forgot the tests for out-of-range enum values :) – Joe Apr 16 '19 at 11:22
@StanislavMolchanovsky If microsoft changes the enumeration values, the most likely result is that *every* program using Outlook interop will have problems. That would be a public interface change. That's not something MS does lightly. – Bradley Uffner Apr 16 '19 at 11:23
@BradleyUffner you are right, it is unlikely. But when choosing a solution it is necessary to consider all its pros and cons :) – smolchanovsky Apr 16 '19 at 11:38

Convert System.DayOfWeek into Microsoft.Office.Interop.Outlook.OlDaysOfWeek

4 Answers4