The fractional part of the milliseconds parameter is the fractional part of a millisecond. For example, 4.5 is equivalent to 4 milliseconds and 5000 ticks, where one millisecond equals 10,000 ticks. However, milliseconds is rounded to the nearest millisecond; all values of .5 or greater are rounded up.
This method returns a new DateTimeOffset object. It does not modify the value of the current object by adding milliseconds to its date and time.
Because a DateTimeOffset object does not represent the date and time in a specific time zone, the AddMilliseconds method does not consider a particular time zone's adjustment rules when it performs date and time arithmetic.
Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)