.net core EF Core DB First

 

项目 框架 是.net 6.0 所以相关依赖最好是6.0以下的

 nuget 安装

Microsoft.EntityFrameworkCore

Microsoft.EntityFrameworkCore.SqlServer

Microsoft.EntityFrameworkCore.Tools

 新建一个数据库 TestDBFirst 建立一个表 User

 新建表语句

USE [TestDBFirst]
GO

/****** Object:  Table [dbo].[User]    Script Date: 2023/4/4 11:33:39 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[User](
    [Id] [int] NOT NULL,
    [Account] [nvarchar](50) NULL,
    [Password] [nvarchar](50) NULL,
    [Name] [nvarchar](50) NULL,
    [Sex] [int] NULL,
    [Status] [int] NULL,
 CONSTRAINT [PK_User] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO

 此时 可以通过语句 生成 对应的实体

Scaffold-DbContext "server=localhost;database=TestDBFirst;uid=sa;pwd=你的密码;" Microsoft.EntityFrameworkCore.SqlServer -o Models -f

在程序包管理平台执行

 

 结果

 public partial class User
    {
        public int Id { get; set; }
        public string? Account { get; set; }
        public string? Password { get; set; }
        public string? Name { get; set; }
        public int? Sex { get; set; }
        public int? Status { get; set; }
    }

 

 public partial class TestDBFirstContext : DbContext
    {
        public TestDBFirstContext()
        {
        }

        public TestDBFirstContext(DbContextOptions<TestDBFirstContext> options)
            : base(options)
        {
        }

        public virtual DbSet<User> Users { get; set; } = null!;

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. You can avoid scaffolding the connection string by using the Name= syntax to read it from configuration - see https://go.microsoft.com/fwlink/?linkid=2131148. For more guidance on storing connection strings, see http://go.microsoft.com/fwlink/?LinkId=723263.
                optionsBuilder.UseSqlServer("server=localhost;database=TestDBFirst;uid=sa;pwd=;");
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<User>(entity =>
            {
                entity.ToTable("User");

                entity.Property(e => e.Id).ValueGeneratedNever();

                entity.Property(e => e.Account).HasMaxLength(50);

                entity.Property(e => e.Name).HasMaxLength(50);

                entity.Property(e => e.Password).HasMaxLength(50);
            });

            OnModelCreatingPartial(modelBuilder);
        }

        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
    }

如果数据库user表出现修改了

修改完就再执行 

Scaffold-DbContext "server=localhost;database=TestDBFirst;uid=sa;pwd=你的密码;" Microsoft.EntityFrameworkCore.SqlServer -o Models -f

 

 如果 从代码 上修改 实体结构可以使用数据迁移来实现

比如我新增 UserId

 

 只需要在程序包管理平台执行 就能得到结果

add-migration init

update-database

 

联合主键的设置 需要通过Fluent API 设置

  protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<User>(entity =>
            {
                entity.ToTable("User");
                //联合主键
                entity.HasKey(p => new { p.Id, p.UserId });
                entity.Property(e => e.Id).ValueGeneratedNever();

                entity.Property(e => e.Account).HasMaxLength(50);

                entity.Property(e => e.Address).HasMaxLength(50);

                entity.Property(e => e.Name).HasMaxLength(50);

                entity.Property(e => e.Password).HasMaxLength(50);
            });

            OnModelCreatingPartial(modelBuilder);
        }

通过数据迁移 映射到数据库

add-migration key2

update-database

 

 生成报错

To change the IDENTITY property of a column, the column needs to be dropped and recreated.

这是因为修改了 标识列引起的

需要删除 Migrations 的 init 文件

 

 数据库中的User表也需要删除

然后执行 

add-migration key2

update-database

符合主键已经建立好

 

 

Script-Migration

生成脚本迁移

 

 

这是第二种方式 主要用到  [NotMapped]  特性 其实就是 不让ef 映射这个表，就是将之前的表的删除，然后再创建，这种方式比较优雅

实体框架修改主键

 

.net Entity Framework 

修改主键会提示这玩意,需要删除表,然后重建..

To change the IDENTITY property of a column, the column needs to be dropped and recreated.

对于没有数据的表,可以这样解决...

假设表名为   change_table

首先注释掉 

// modelBuilder.Entity<change_table>();

然后..

[NotMapped]  //　　加上这玩意..
[Table("change_table ")]
public partial class change_table {

}

执行命令 

add-migration  删除表change_table 

update-database

然后取消注释,去掉 [NotMapped]  

add-migration  添加表 change_table 

update-database

完事..

对于有主外键引用的.

注释掉 ForeignKey 就可以了..不用注释属性,这样就可以不用改代码了..

对于有数据的表....没啥子想法

 

 

 

  [ConcurrencyCheck] 做并发检查特性

 下面也是做并发检查

[Timestamp]  
public byte[] RowVesion { get; set; }

表名

[Column("Phone")]

  public partial class User
    {
        [Key]
        public int Id { get; set; }

        [Key]
        public int UserId { get; set; }

        public string? Account { get; set; }
        public string? Password { get; set; }
        [ConcurrencyCheck]
        public string? Name { get; set; }
        public int? Sex { get; set; }
        public int? Status { get; set; }
        public string? Address { get; set; }

        [Timestamp]
        public byte[] RowVesion { get; set; }
    }