Area类

public virtual User User { get; set; }

User类

public virtual Area Area { get; set; }

Context类

modelBuilder.Entity<Area>()                        //巡检区域-区域负责人

.HasOptional(a => a.User)

.WithOptionalDependent()

.Map(x => x.MapKey("UserID"));

modelBuilder.Entity<User>()                        //巡检区域-区域负责人

.HasOptional(u => u.Area)

.WithOptionalDependent()

.Map(x => x.MapKey("AreaID"));