OnModelBuilding作用

1. 初始化数据

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<ModelA>().HasData(param[] ModelA);//HasData括号内为添加的数据。ModelA是Model对象
            modelBuilder.Entity<ModelB>().HasData(param[] ModelB);//HasData括号内为添加的数据。ModelB是Model对象
            base.OnModelCreating(modelBuilder);
        }

2. 定义FluentAPI
   参考https://www.cnblogs.com/seekdream/p/10641510.html