.net 根據輸入日期得到當前所在周的周一（可延伸獲取周的任何一天）

思想：主要根據DateTime類的DayOfWeek屬性來得到周的英文名字，然后通過日期天數的加減運算得到周一。

1.調用：

string today = "2015-7-13";//System.DateTime.Now.ToString(); lblDay.Text = GetMondayOfTheWeek(today);

2.方法：

PRivate string GetMondayOfTheWeek(string today) { string sMonday = ""; DateTime dateNow; try{ dateNow= Convert.ToDateTime(today); } catch { sMonday="方法GetMondayOfWeeks傳入的參數格式錯誤，請檢查后重新調用！"; return sMonday; } string dayOfWeekName = dateNow.DayOfWeek.ToString(); int day=0; switch(dayOfWeekName) { case "Monday": day= 0; break; case "Tuesday": day= 1; break; case "Wednesday": day= 2; break; case "Thursday": day= 3; break; case "Friday": day= 4; break; case "Saturday": day= 5; break; case "Sunday": day=6; break; } sMonday = dateNow.AddDays(-day).ToString("yyyy-M-d"); return sMonday; }