Creating Calendar Rules in Microsoft Dynamics CRM 2016

/// <summary>
/// Creates the calender.
/// </summary>
/// <param name="service">The service.</param>
/// <param name="bookableResourceId">The bookable resource identifier.</param>
/// <param name="startTime">The start time.</param>
/// <param name="durationInMinutes">The duration in minutes.</param>
private static void CreateCalender(IOrganizationService service, Guid bookableResourceId, DateTime startTime, int durationInMinutes)
{
    using (var context = new CrmServiceContext(service))
    {
        var bookableResource = context.BookableResourceSet.Where(b => b.Id == bookableResourceId).FirstOrDefault();

        // Get the user calendar
        var calendar = context.CalendarSet.First(r => r.Id == bookableResource.CalendarId.Id);

        // Retrieve the calendar of the user
        Entity userCalendarEntity = service.Retrieve("calendar", calendar.Id, new ColumnSet(true));

        // Retrieve the calendar rules defined in the calendar
        EntityCollection calendarRules = (EntityCollection)userCalendarEntity.Attributes["calendarrules"];

        // Create a new inner calendar
        Entity newInnerCalendar = new Entity("calendar");
        newInnerCalendar.Attributes["businessunitid"] = new EntityReference("businessunit", ((Microsoft.Xrm.Sdk.EntityReference)(userCalendarEntity["businessunitid"])).Id);
        Guid innerCalendarId = service.Create(newInnerCalendar);

        // Create a new calendar rule and assign the inner calendar id to it
        Entity calendarRule = new Entity("calendarrule");
        //calendarRule.Attributes["duration"] = durationInMinutes;
        calendarRule.Attributes["duration"] = 1440; // 24hrs in minutes
        //It specifies the extent of the Calendar rule,generally an Integer value.
        calendarRule.Attributes["effort"] = 1.0;

        calendarRule.Attributes["extentcode"] = 1;
        calendarRule.Attributes["pattern"] = "FREQ=DAILY;COUNT=1";
        //Rank is an Integer value which specifies the Rank value of the Calendar rule
        calendarRule.Attributes["rank"] = 0;
        // Timezone code to be set which the calendar rule will follow
        calendarRule.Attributes["timezonecode"] = bookableResource.TimeZone;
        //Specifying the InnerCalendar Id
        calendarRule.Attributes["innercalendarid"] = new EntityReference("calendar", innerCalendarId);

        //Start time for the created Calendar rule
        calendarRule.Attributes["starttime"] = startTime.Date;

        calendarRules.Entities.Add(calendarRule);

        // assign all the calendar rule back to the user calendar
        userCalendarEntity.Attributes["calendarrules"] = calendarRules;
        // update the user calendar entity that has the new rule
        service.Update(userCalendarEntity);

        // Calendar rule for Working Day 
        Entity workingHourcalendarRule = new Entity("calendarrule");
        workingHourcalendarRule.Attributes["duration"] = durationInMinutes;
        //Effort available for a resource (User) during the time described by the calendar rule i.e. Capacity part in the Calendar rule
        workingHourcalendarRule.Attributes["effort"] = 1.0;
        // It is a Flag used in vary-by-day calendar rules.
        workingHourcalendarRule.Attributes["issimple"] = true;

        workingHourcalendarRule.Attributes["offset"] = startTime.Hour * 60 + startTime.Minute; //to indicate start time
        //Rank of the Calendar Rule
        workingHourcalendarRule.Attributes["rank"] = 0;
        //Sub Type of the Calendar rule.For setting Work hours it is 1.
        workingHourcalendarRule.Attributes["subcode"] = 1;
        //Type of calendar rule such as working hours, break, holiday, or time off. 0 for working hours
        workingHourcalendarRule.Attributes["timecode"] = 0;
        // Local time zone for the calendar rule.
        workingHourcalendarRule.Attributes["timezonecode"] = -1;
        //Specifying the InnerCalendar Id
        workingHourcalendarRule.Attributes["calendarid"] = new EntityReference("calendar", innerCalendarId);

        EntityCollection innerCalendarRules = new EntityCollection();
        innerCalendarRules.EntityName = "calendarrule";
        innerCalendarRules.Entities.Add(workingHourcalendarRule);

        newInnerCalendar.Attributes["calendarrules"] = innerCalendarRules;
        newInnerCalendar.Attributes["calendarid"] = innerCalendarId;
        service.Update(newInnerCalendar);
    }
}