c#
// no issues with this code?
public bool addUser(User user){
            if(user == null){
                throw new ArgumentNullException("Cannot have null values");
            }
            try
            {
                // check to see if there is a user with the same username in db
                User user_check = _context.Users.Where(u => u.Id == user.Id).FirstOrDefault();
                if (user_check != null)
                {
                    throw new Exception("User already exists");
                }
                // will add the user to the database + save changes to commit them.
                _context.Users.Add(user);
                _context.SaveChanges(); // gets added succesfully
                return true;
            }
            catch (Exception e)
            {
                throw new Exception($"Failed to add user to database {e}");
            }
        }

c#
// no issues with this code?
public bool addUser(User user){
            if(user == null){
                throw new ArgumentNullException("Cannot have null values");
            }
            try
            {
                // check to see if there is a user with the same username in db
                User user_check = _context.Users.Where(u => u.Id == user.Id).FirstOrDefault();
                if (user_check != null)
                {
                    throw new Exception("User already exists");
                }
                // will add the user to the database + save changes to commit them.
                _context.Users.Add(user);
                _context.SaveChanges(); // gets added succesfully
                return true;
            }
            catch (Exception e)
            {
                throw new Exception($"Failed to add user to database {e}");
            }
        }