Q:

Getting a Sharepoint List Fields that are common to all content types contained in the list

I'm trying to get the list fields shared by all the content types in said List. 
After getting the List by its Title, I used the Fields property to get all the fields in the List: 
List list = clientContext. Web. Lists. GetByTitle('list Title');
clientContext. Load(list);
FieldCollection listFields = list. Fields;
clientContext. Load(listFields);

The problem is I only want the ones shared by all content types in the list. 
Is there a way to get them without having to go through all the content types and their respective Fields and comparing them to get the one in common? 

A:

As far as I know, you can't tell which Content Type it is from Field object

