asp.net core EF code first

以连接mysql数据库为例

一 安装组件

Microsoft.EntityFrameworkCore

Microsoft.EntityFrameworkCore.Relational

Microsoft.EntityFrameworkCore.Tools

MySqlConnector

Pomelo.EntityFrameworkCore.MySql

二 新增MySQLDbContext,继承自DbContext,并新增一个数据库表实体Article

　　[Table("Articles")]
    public class Article
    {
        /// <summary>
        /// 主键id
        /// </summary>
        [Key]
        public string Id { get; set; }

        /// <summary>
        /// 标题
        /// </summary>
        public string Title { get; set; }

        /// <summary>
        /// 内容
        /// </summary>
        [MaxLength(255)]
        public string Content { get; set; }

        /// <summary>
        /// 创建时间
        /// </summary>
        public DateTime CreatedDT { get; set; }

        /// <summary>
        /// 修改时间
        /// </summary>
        public DateTime ModifiedDT { get; set; }
    }

    public class MySQLDbContext : DbContext
    {
        public MySQLDbContext(DbContextOptions<MySQLDbContext> options) : base(options) { }

        public DbSet<Article> ArticleSets { get; set; }

        //...
    }

　　

三 appsettings配置数据库连接字符串,并在Startup.cs中添加服务

Startup.cs:

services.AddDbContext<MySQLDbContext>(options => options.UseMySql(Configuration.GetConnectionString("MySQL")));

　注:字符串连接名称"MySQL"与appsettings中配置的名称对应.

四 code first方式创建数据库

1.程序包管理控制台PM命令

 remove-migrations
 add-migrations my-gration
 update-database

2.donet命令行

 dotnet ef migrations remove
 dotnet ef migrations add my-gration
 dotnet ef database update

3.代码内执行创建数据库的代码(EnsureCreated)

新增DbContextExtension扩展类EnsureCreatedDB扩展方法:

 public static IWebHost EnsureCreatedDB<TContext>(this IWebHost host) where TContext : DbContext
 {
     using (var scope = host.Services.CreateScope())
     {
     　　var context = scope.ServiceProvider.GetService<TContext>();
     　　context.Database.EnsureCreated();
     }
     return host;
 }

在Program.cs中调用该扩展方法:

 public static void Main(string[] args)
 {
     CreateWebHostBuilder(args).Build()
     .EnsureCreatedDB<MySQLDbContext>()  //调用扩展方法
     .Run();
 }

五 使用EF进行增删改查

     [ApiController]
     [Route("api-hd/article")]
     public class ArticleController : ControllerBase
     {
         private MySQLDbContext _dbContext;

         public ArticleController(MySQLDbContext dbContext)
         {
             _dbContext = dbContext;
         }

         /// <summary>
         /// 新增文章
         /// </summary>
         /// <param name="title"></param>
         /// <param name="content"></param>
         /// <returns></returns>
         [AllowAnonymous]
         [HttpPost]
         [Route("")]
         public async Task<bool> Add(string title, string content)
         {
             var newArticle = new Article()
             {
                 Id = Guid.NewGuid().ToString(),
                 Title = title,
                 Content = content,
                 CreatedDT = DateTime.Now,
                 ModifiedDT = DateTime.Now,
             };
             await _dbContext.AddAsync(newArticle);
             await _dbContext.SaveChangesAsync();
             return true;
         }

         /// <summary>
         /// 根据id查询文章
         /// </summary>
         /// <param name="id"></param>
         /// <returns></returns>
         [AllowAnonymous]
         [HttpGet]
         [Route("{id}")]
         public async Task<Article> GetById(string id)
         {
             var data = await _dbContext.ArticleSets.FindAsync(id);
             return data;
         }

         /// <summary>
         /// 更新文章标题
         /// </summary>
         /// <param name="id"></param>
         /// <param name="title"></param>
         /// <returns></returns>
         [AllowAnonymous]
         [HttpPut]
         [Route("")]
         public async Task<bool> Update(string id, string title)
         {
             var existArticle = await _dbContext.ArticleSets.FindAsync(id);
             if (existArticle == null)
             {
                 return false;
             }

             existArticle.Title = title;
             //_dbContext.Update(existArticle);
             await _dbContext.SaveChangesAsync();
             return true;
         }

         /// <summary>
         /// 根据id删除文章
         /// </summary>
         /// <param name="id"></param>
         /// <returns></returns>
         [AllowAnonymous]
         [HttpDelete]
         [Route("{id}")]
         public async Task<bool> Delete(string id)
         {
             var existArticle = await _dbContext.ArticleSets.FindAsync(id);
             if (existArticle == null)
             {
                 return false;
             }

             _dbContext.Remove(existArticle);
             await _dbContext.SaveChangesAsync();
             return true;
         }

     }