Thanks for your answer Walaa,
The .cs class was not in the project. It was probably in the folder but I didn't think of trying to include it. I tried to remove and re-set references without success. I then remove all the project from my solution and re-generate the code. It was then working.
Note: Next time, if it re-happen, I will look at the missing file in the folder. It will surely be there and it will be less trouble. Good Idea, thanks !
Everything is ok now.
Thanks.