Look at your code:
EmailAddress += employee.ArtifactID + favouriteDocumentsField.Name + "Object: " + index, docID);
What is the end of that doing?
If I cut it down a bit it'll be clearer:
EmailAddress += "a string", docID);
What do you expect the compiler to do with the command and the stuff to it's right?
Probably, what you meant was:
EmailAddress += employee.ArtifactID + favouriteDocumentsField.Name + "Object: " + index + docID;
But you need to think about what you are doign as that won't work either, given that the line is inside a loop and will concatenate all the "email addresses" together:
joe@gmail.commike@gmail.com@sara@mydomain.co.in