C#.NET 日期操作类

 

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace Pub.Class
{
    /// <summary>
    /// 日期操作类
    /// </summary>
    public class Date
    {

        #region ExactTimeSpan
        /// <summary>
        /// 精确的时间差
        /// </summary>
        /// <example>
        /// <code>
        /// context.items["beginrequesttickcount"]=a.gettickcount();
        /// 代码段
        /// new TimeSpan(A.GetTickCount()-(long)Context.Items["BeginRequestTickCount"]).TotalMilliseconds
        /// </code>
        /// </example>
        public class ExactTimeSpan { 
            [DllImport("kernel32.dll")]
            static extern bool QueryPerformanceCounter([In, Out] ref long lpPerformanceCount);
            [DllImport("kernel32.dll")]
            static extern bool QueryPerformanceFrequency([In, Out] ref long lpFrequency);
            static long _f = 0;
            /// <summary>
            /// 来纪录程序开始时的TickCount
            /// </summary>
            /// <returns>TickCount</returns>
            static public long GetTickCount() {
                long f = _f;
                if (f == 0)
                    if (QueryPerformanceFrequency(ref f)) _f = f; else _f = -1;

                if (f == -1)  return Environment.TickCount * 10000;
                long c = 0;
                QueryPerformanceCounter(ref c);
                return (long)(((double)c) * 1000 * 10000 / ((double)f));
            }

            static long _tc = 0;//GetTickCount()为0时的DateTime.Ticks值

            /// <summary>
            /// 这个返回的不是真正的精确时间，但时间与时间的差是精确的。
            /// GetExactNow与DateTime.Now的偏差比DateTime.Now的精度还要小
            /// </summary>
            /// <returns>时间与时间差</returns>
            static public DateTime GetExactNow() {
                if (_tc == 0) {
                    long tc = GetTickCount();
                    DateTime dt = DateTime.Now;
                    _tc = dt.Ticks - tc;
                    return dt;
                }
                return new DateTime(_tc + GetTickCount());
            }
        }
        #endregion

    }
}