怎么获得本周周一的时间啊？求高手

Question

比如今天18号，星期五，我要获得周一的时间就是14号，怎么得到？是不是要循环？求高手

Answer 1

          DateTime datetime = Convert.ToDateTime(year + "-" + month + "-" + "1");
            // MessageBox.Show(datetime.DayOfWeek + "");
            int week = 0;
            switch (datetime.DayOfWeek)
            {
                case DayOfWeek.Friday:
                    week = 5;
                    break;
                case DayOfWeek.Monday:
                    week = 1;
                    break;
                case DayOfWeek.Saturday:
                    week = 6;
                    break;
                case DayOfWeek.Sunday:
                    week = 7;
                    break;
                case DayOfWeek.Thursday:
                    week = 4;
                    break;
                case DayOfWeek.Tuesday:
                    week = 2;
                    break;
                case DayOfWeek.Wednesday:
                    week = 3;
                    break;
                default:
                    week = 0;
                    break;
            }
知道今天是星期几了。
例如星期5 
int 星期5=5；
int 星期一=1；
5-1=4；
18-4=14；

Answer 2

SELECT  DATEADD(wk,  DATEDIFF(wk,0,getdate()),  0)  

Answer 3

 DateTime dt = DateTime.Now;
            int days=(int)dt.DayOfWeek-(int)(DayOfWeek.Monday);
            DateTime monday_date=dt.AddDays(-days);
            //+ monday_date {2011-11-14 12:37:13} System.DateTime