No person shall seek beg or solicit custom, patronage, sales, alms or donations for himself or on behalf of any person in any manner or for any purpose in any building or in or on any property or premises under the control of this City without the written permission of the head of the department having jurisdiction over the building or grounds where such solicitation is to be made. Where solicitation is to be made of employees of a department within the offices and spaces in public buildings assigned to that department, such solicitation is prohibited unless permission is obtained from the head of the department.