We add a composite unique constraint and a new Model class in a 1:0 or m relationship to Patient.br 1:00 Composite Unique Constraintbr 4:00 Add to Catch for DbUpdateExceptionbr 8:15 Medical Trial Modelbr 10:30 Nullable Foreign Key propertiesbr 11:40 DbContext - Cascade Delete?br 13:35 Database Initializerbr 16:53 Seed Databr 19:30 Changes to the UIbr 20:45 Modify Viewsbr 25:15 Controller Changes, Select Listsbr 28:45 .