EF Core DBFirst和CodeFirst 模式使用方法

一、安装依赖包

1、Microsoft.EntityFrameworkCore

2、Microsoft.EntityFrameworkCore.Tools

3、Microsoft.EntityFrameworkCore.SqlServer

二、模式选择

1、DBFirst 模式

1）新建数据库脚本并执行

2）打开程序包管理控制台生成DbContext上下文以及实体Model

scaffold-dbcontext "server=.;database=dbfirst;uid=sa;pwd=123456;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

3）配置Startup 类注册DbContext上下文

services.AddDbContext<CodeFirstContext>(options =>
{
    options.UseSqlServer(Configuration.GetConnectionString("ConStr"));
});

4）配置appsettings.json文件

"ConnectionStrings": {
    "ConStr": "Server=localhost;Database=CodeFirst;Uid=sa;Pwd=Dennis374627149;"
  }

5）Controller中依赖注入就可以使用了

private readonly DbContextOptions<CodeFirstContext> _context;

public WeatherForecastController(ILogger<WeatherForecastController> logger, DbContextOptions<CodeFirstContext> context)
{
    _logger = logger;
    _context = context;
}

using (var context = new CodeFirstContext(_context))
{
    var model = context.UserEntities.FirstOrDefault(p => p.UserId.Equals("14"));
    if (model != null) return model.UpdateTime.ToString();
    return "";
}

2、Code First 模式

1）新建实体类Model

[Table("Users")]
public class UserEntity
{
    [Key]
    [Required]
    [StringLength(32)]
    public string UserId { get; set; }

    [Required]
    [StringLength(20)]
    public string Name { get; set; }
    [StringLength(20)]
    public int Age { get; set; }
    [StringLength(11)]
    public string Tel { get; set; }
    [StringLength(11)]
    public DateTime Birthday { get; set; }

    [Required]
    public DateTime CreateTime { get; set; }
    [Required]
    public DateTime UpdateTime { get; set; } = DateTime.Now;
}

2）新建DbContext上下文类，继承DbContext

public class CodeFirstContext:DbContext
{
    public CodeFirstContext()
    {
    }
    public CodeFirstContext(DbContextOptions<CodeFirstContext> options) : base(options)
    {
    }
    public DbSet<UserEntity> UserEntities { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
    }
}

3）Startup注入和appsettting.json文件同上

4）打开程序包控制台（CodeFirstTest 自定义名称，如提示To undo this action, use Remove-Migration 代表初始化成功）

Add-Migration CodeFirstTest

5）继续（更新最后一次迁移）

update-database

6）迁移完成