The hard-part is "without using third party libraries". What, not even open-source?
Actually, the issue is very simple. You don't want to use any third party library. All right, but you still need a library. As .NET FCL does not have the library supporting the multipage TIFF feature, you have to write such library by yourself.
Well, try this CodeProject work:
Save images into a multi-page TIFF file or add images to an existing TIFF file[
^].
The delicate question is: if you use this code and it will help you, will you consider yourself using a 3rd-party library or not? :-)
If it is a problem or my notes makes you thinking about it, still consider this open-source library:
http://bitmiracle.com/libtiff/[
^].
Just in case you wanted to think about it.
—SA