using System;
using System.Collections.Generic;
//using System.Linq;
using System.Text;

namespace WebSqlHelper
{
    public class DateHelper
    {
        public static string dateFormat(string date, string format)
        {
            string str = "";
            if (!string.IsNullOrEmpty(date))
            {
                try
                {
                    str = DateTime.Parse(date).ToString(format);
                }
                catch
                { }
            }
            return str;
        }
        /// <summary> 
        /// 计算本周的周一日期 
        /// </summary> 
        /// <returns></returns> 
        public static DateTime GetMondayDate()
        {
            return GetMondayDate(DateTime.Now);
        }
        /// <summary> 
        /// 计算本周周日的日期 
        /// </summary> 
        /// <returns></returns> 
        public static DateTime GetSundayDate()
        {
            return GetSundayDate(DateTime.Now);
        } 
        /// <summary> 
        /// 计算某日起始日期（礼拜一的日期） 
        /// </summary> 
        /// <param name="someDate">该周中任意一天</param> 
        /// <returns>返回礼拜一日期，后面的具体时、分、秒和传入值相等</returns> 
        public static DateTime GetMondayDate(DateTime someDate)
        {
            int i = someDate.DayOfWeek - DayOfWeek.Monday;
            if (i == -1) i = 6;// i值 > = 0 ，因为枚举原因，Sunday排在最前，此时Sunday-Monday=-1，必须+7=6。 
            TimeSpan ts = new TimeSpan(i, 0, 0, 0);
            return someDate.Subtract(ts);
        }
        /// <summary> 
        /// 计算某日结束日期（礼拜日的日期） 
        /// </summary> 
        /// <param name="someDate">该周中任意一天</param> 
        /// <returns>返回礼拜日日期，后面的具体时、分、秒和传入值相等</returns> 
        public static DateTime GetSundayDate(DateTime someDate)
        {
            int i = someDate.DayOfWeek - DayOfWeek.Sunday;
            if (i != 0) i = 7 - i;// 因为枚举原因，Sunday排在最前，相减间隔要被7减。 
            TimeSpan ts = new TimeSpan(i, 0, 0, 0);
            return someDate.Add(ts);
        } 
    }
}