If you say the error is at:
Quote:
cb.eNtsaCourse.Add(eNtsaCourses.Courses);
eNtsaCourses.Courses seems to be the culprit. Mostly, eNtsaCourses is null.
OR
eNtsaCourses.Courses is null.
While trying to save the value null for Courses, it throws an error. (Error at DTO/Entity level)
You need to:
1. make sure that the request holds the value if it is supposed to
2. Irrespective of request, your code should handle validations around input to avoid such errors.