how to convert combat log guid to int128 guid ?

What do you mean? Guid128 has a constructor that takes Int128 and the ToString method parses it to ingame GUID names.
Whatever you want to do, you can work with that. 

If you want to parse the string to a Guid 128, you would need to fill the respective bits of a 128 bit integer. I haven't done that so have no example code

Yes i know what u mean but what i want is how to convert ingame guid to hex128bit. 

Nvm i found my answer on other forum.

Then please post the answer here as well.