2013 年 6 月 1 日更新
我开发了一种扩展方法来解决这个特定问题，并且我在下面发布了该代码。我希望它可以帮助某人。
背景
我的任务是向应用程序添加功能，以允许设置定期会议（与 Outlook 完全相同）。
因此，例如，用户可能希望在每个月的第一个星期五、或每个月的最后一个星期一、或每个月的第二个工作日等召开会议。
是否存在用于此的标准算法？我找到了很多部分答案，但是没有什么可以允许像这样的干净扩展方法：
/// <summary>
/// Accepts a date object and finds the next date given an ordinality and type.
/// </summary>
/// <param name="ordinality">The ordinality (e.g. "first", "second", "last", etc.)</param>
/// <param name="dayType">The day type (e.g. "weekday", "Monday", "day", etc)</param>
/// <returns>A new date object</returns>
public static DateTime GetNextDateOfType(this DateTime date, string ordinality, string dayType)
{
//do stuff
return newDate;
}
我一直在断断续续地做这件事，但我一直在想肯定已经有一些东西了。
到目前为止我所拥有的：
public static DateTime GetNextDateOfType(this DateTime date, string ordinality, string dayType)
{
var dateTest = new DateTime(date.Year, date.Month, 1);
var dateFound = false;
var ordinal = 1;
var targetOrdinal = ordinality.ToOrdinal();
while (!dateFound)
{
//Test for type:
switch (dayType)
{
case "day":
if (dateTest >= date)
{
if (ordinality == "last" && dateTest == dateTest.GetLastDayOfMonth() || dateTest.Day == targetOrdinal)
{
dateFound = true;
}
}
break;
case "weekday":
if (dateTest >= date && dateTest.IsWeekDay())
{
if (targetOrdinal == ordinal)
{
dateFound = true;
}
ordinal++;
}
break;
case "weekend day":
if (dateTest >= date && !dateTest.IsWeekDay())
{
dateFound = true;
}
break;
default:
if (dateTest >= date && dateTest.DayOfWeek == HelperMethods.GetDayOfWeekFromString(dayType))
{
dateFound = true;
}
break;
}
dateTest = dateTest.AddDays(1);
}
return dateTest;
}
public static DateTime GetLastDayOfMonth(this DateTime date)
{
return new DateTime(date.Year, date.Month, DateTime.DaysInMonth(date.Year, date.Month));
}
public static int ToOrdinal(this string ordinal)
{
var result = 0;
switch (ordinal.ToLower())
{
case "first":
result = 1;
break;
case "second":
result = 2;
break;
case "third":
result = 3;
break;
case "fourth":
result = 4;
break;
case "fifth":
result = 5;
break;
default:
result = -1;
break;
}
return result;
}
public static bool IsWeekDay(this DateTime date)
{
var weekdays = new List<DayOfWeek>
{
DayOfWeek.Monday,
DayOfWeek.Tuesday,
DayOfWeek.Wednesday,
DayOfWeek.Thursday,
DayOfWeek.Friday
};
return weekdays.Contains(date.DayOfWeek);
}
public static List<DateTime> GetWeeks(this DateTime month, DayOfWeek startOfWeek)
{
var firstOfMonth = new DateTime(month.Year, month.Month, 1);
var daysToAdd = ((Int32)startOfWeek - (Int32)month.DayOfWeek) % 7;
var firstStartOfWeek = firstOfMonth.AddDays(daysToAdd);
var current = firstStartOfWeek;
var weeks = new List<DateTime>();
while (current.Month == month.Month)
{
weeks.Add(current);
current = current.AddDays(7);
}
return weeks;
}
public static int GetWeekOfMonth(this DateTime date)
{
var beginningOfMonth = new DateTime(date.Year, date.Month, 1);
while (date.Date.AddDays(1).DayOfWeek != CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
date = date.AddDays(1);
return (int)Math.Truncate((double)date.Subtract(beginningOfMonth).TotalDays / 7f) + 1;
}