用 C# 计算 与 java 一致的unix时间戳 （长时间整形 如：1476956079961）

背景：

调用java提供接口，需要长时间整形作为验证。

预备知识：

1、 java 的 System.currentTimeMillis() 计算的长整型，是从1970年1月1日开始，截止当前的毫秒数。

2、C#中计算毫秒数的方法 TimeSpan.TotalMilliseconds

3、我天朝是东八区，时区也要计算在内。所以起始期间应为1970年1月1日8：00

代码：

        /// <summary>
        /// 计算当前长时间整形  
        /// </summary>
        private long GetTimeLong()
        {
            var javaLongTime = new DateTime(, , , , , );   
            var now = DateTime.Now;
            var interval = now - javaLongTime;
            return (long)interval.TotalMilliseconds;   

        }    

扩展：

TimeSpan 除了毫秒总数，其他时间单位：

// Define two dates.
DateTime date1 = new DateTime(2010, 1, 1, 8, 0, 15);
DateTime date2 = new DateTime(2010, 8, 18, 13, 30, 30);
// Calculate the interval between the two dates.
TimeSpan interval = date2 - date1;
Console.WriteLine("{0} - {1} = {2}", date2, date1, interval.ToString());
// Display individual properties of the resulting TimeSpan object.
Console.WriteLine("   {0,-35} {1,20}", "Value of Days Component:", interval.Days);
Console.WriteLine("   {0,-35} {1,20}", "Total Number of Days:", interval.TotalDays);
Console.WriteLine("   {0,-35} {1,20}", "Value of Hours Component:", interval.Hours);
Console.WriteLine("   {0,-35} {1,20}", "Total Number of Hours:", interval.TotalHours);
Console.WriteLine("   {0,-35} {1,20}", "Value of Minutes Component:", interval.Minutes);
Console.WriteLine("   {0,-35} {1,20}", "Total Number of Minutes:", interval.TotalMinutes);
Console.WriteLine("   {0,-35} {1,20:N0}", "Value of Seconds Component:", interval.Seconds);
Console.WriteLine("   {0,-35} {1,20:N0}", "Total Number of Seconds:", interval.TotalSeconds);
Console.WriteLine("   {0,-35} {1,20:N0}", "Value of Milliseconds Component:", interval.Milliseconds);
Console.WriteLine("   {0,-35} {1,20:N0}", "Total Number of Milliseconds:", interval.TotalMilliseconds);
Console.WriteLine("   {0,-35} {1,20:N0}", "Ticks:", interval.Ticks);
// the example displays the following output:
//       8/18/2010 1:30:30 PM - 1/1/2010 8:00:15 AM = 229.05:30:15
//          Value of Days Component:                             229
//          Total Number of Days:                   229.229340277778
//          Value of Hours Component:                              5
//          Total Number of Hours:                  5501.50416666667
//          Value of Minutes Component:                           30
//          Total Number of Minutes:                       330090.25
//          Value of Seconds Component:                           15
//          Total Number of Seconds:                      19,805,415
//          Value of Milliseconds Component:                       0
//          Total Number of Milliseconds:             19,805,415,000
//          Ticks:                               198,054,150,000,000

参见：https://msdn.microsoft.com/en-us/library/system.timespan(v=vs.110).aspx