Unix时间戳与C# DateTime时间类型互换

/// <summary>
/// method for converting a System.DateTime value to a UNIX Timestamp
/// </summary>
/// <param name="value">date to convert</param>
/// <returns></returns>
private double ConvertToTimestamp(DateTime value)
{
    //create Timespan by subtracting the value provided from
    //the Unix Epoch
    TimeSpan span = (value - new DateTime(1970, 1, 1, 0, 0, 0, 0).ToLocalTime());

    //return the total seconds (which is a UNIX timestamp)
    return (double)span.TotalSeconds;
}