C#中实现随机时间的获取

    原理其实非常简单，取出两个时间差的秒数，再在0到该秒数之间随机获取一个整数，将其做为秒添加到较小的时间上，可以说实现上并没什么技术难点，可以在数据类型的边界条件上却需要格外的注意，比如将大于 system.int32.maxvalue 或小于 system.int32.minvalue 的值转成 int 时，如果直接在变量前加上类型名转换（(int)d），不会有有异常产生，但得到的值却是 system.int32.minvalue，还有就是对于math.abs 方法，当参数 value 等于 minvalue 将会引发 system.overflowexception 异常。

代码如下：

using system;

namespace yyw
{
    public class datetimehelper
    {
        /**//// <summary>
        /// 获取随机时间
        /// <remarks>
        /// 由于random 以当前系统时间做为种值,所以当快速运行多次该方法所得到的结果可能相同,
        /// 这时,你应该在外部初始化 random 实例并调用 getrandomtime(datetime time1, datetime time2, random random)
        /// </remarks>
        /// </summary>
        /// <param name="time1"></param>
        /// <param name="time2"></param>
        /// <returns></returns>
        public static datetime getrandomtime(datetime time1, datetime time2)
        {
            random random = new random();
            return getrandomtime(time1, time2, random);
        }

        /**//// <summary>
        /// 获取随机时间
        /// </summary>
        /// <param name="time1"></param>
        /// <param name="time2"></param>
        /// <param name="random"></param>
        /// <returns></returns>
        public static datetime getrandomtime(datetime time1, datetime time2, random random)
        {
            datetime mintime = new datetime();
            datetime maxtime = new datetime();

            system.timespan ts = new system.timespan(time1.ticks - time2.ticks);

            // 获取两个时间相隔的秒数
            double dtotalsecontds = ts.totalseconds;
            int itotalsecontds = 0;

            if (dtotalsecontds > system.int32.maxvalue)
            {
                itotalsecontds = system.int32.maxvalue;
            }
            else if (dtotalsecontds < system.int32.minvalue)
            {
                itotalsecontds = system.int32.minvalue;
            }
            else
            {
                itotalsecontds = (int)dtotalsecontds;
            }

            if (itotalsecontds > 0)
            {
                mintime = time2;
                maxtime = time1;
            }
            else if (itotalsecontds < 0)
            {
                mintime = time1;
                maxtime = time2;
            }
            else
            {
                return time1;
            }

            int maxvalue = itotalsecontds;

            if (itotalsecontds <= system.int32.minvalue)
                maxvalue = system.int32.minvalue + 1;

            int i = random.next(system.math.abs(maxvalue));

            return mintime.addseconds(i);
        }
    }
}
测试代码：

using system;
using nunit.framework;

namespace yyw
{
    [testfixture]
    public class datetimehelperfixture
    {
        /**//// <summary>
        /// 边界测试
        /// </summary>
        [test]
        public void testgetrandomtime()
        {
            datetime mintime = datetime.minvalue;
            datetime maxtime = datetime.maxvalue;
            random random = new random();

            for (int i = 0; i < 10000; i++)
            {
                datetime randomtime = datetimehelper.getrandomtime(maxtime, mintime, random);
                checkresult(mintime, maxtime, randomtime);
            }

            for (int i = 0; i < 10000; i++)
            {
                datetime randomtime = datetimehelper.getrandomtime(mintime, maxtime, random);
                checkresult(mintime, maxtime, randomtime);
            }
        }

        private void checkresult(datetime mintime, datetime maxtime, datetime randomtime)
        {
            system.timespan ts1 = new system.timespan(randomtime.ticks - mintime.ticks);
            system.timespan ts2 = new system.timespan(randomtime.ticks - maxtime.ticks);
            assert.istrue(ts1.seconds >= 0 && ts2.seconds <= 0);
        }
    }
}