Robert Leased an Apartment from Universal Apartments for $600 Per

Robert leased an apartment from Universal Apartments for $600 per month,signing a one-year lease.After two months,Robert's employer transferred him out-of-state,so Robert cannot use the apartment anymore.However,Robert's friend Sam would like to take over the apartment.Robert would like to assign his lease to Sam,but the lease contains a clause that allows assignment only with the consent of the landlord.The landlord refuses to consent to the assignment,because he could now end Robert's lease and rent the apartment for $800 per month.Sam would be just as good a tenant as Robert.Discuss the validity of the anti-assignment clause.