设置EntityFramework 在开发时自动更新数据库

using Libaray.Models.Entities;
using Libaray.Models.Maps;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Libaray.DAL
{
    public class LibarayContext : DbContext
    {
        public LibarayContext(): base("name = LibCon")
        {
            Database.SetInitializer(new MigrateDatabaseToLatestVersion<LibarayContext, Libaray.DAL.Migrations.Configuration>()); //重要
        }

        public DbSet<UserModel> UserModels { get; set; }
        public DbSet<UserInRoleModel> UserInRoleModels { get; set; }
        public DbSet<UserRoleModel> UserRoleModels { get; set; }
        public DbSet<BookModel> BookModels { get; set; }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Configurations.Add(new UserInRoleModelMap());
            modelBuilder.Configurations.Add(new UserRoleModelMap());
            modelBuilder.Configurations.Add(new UserModelMap());
            modelBuilder.Configurations.Add(new BookModelMap());
        }
    }
}

namespace Libaray.DAL.Migrations
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    using System.Linq;

    internal sealed class Configuration : DbMigrationsConfiguration<Libaray.DAL.LibarayContext>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = true;
            AutomaticMigrationDataLossAllowed = true;
        }

        protected override void Seed(Libaray.DAL.LibarayContext context)
        {

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Libaray.Models.Entities
{
    public class BookModel
    {
        public Guid BookId { get; set; }
        public string BookName { get; set; }
        public string Author { get; set; }
        public string BookDescription { get; set; }
        public DateTime BookDate { get; set; }
        public DateTime CreatedOn { get; set; }
        public Guid CreatedBy { get; set; }
        public DateTime UpdatedOn { get; set; }
        public Guid UpdatedBy { get; set; }
    }
}

using Libaray.Models.Entities;
using System;
using System.Collections.Generic;
using System.Data.Entity.ModelConfiguration;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Libaray.Models.Maps
{
    public class BookModelMap : EntityTypeConfiguration<BookModel>
    {
        public BookModelMap()
        {
            this.HasKey(u => u.BookId);
            this.Property(u => u.BookId).HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity);
        }
    }
}