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;
        }
        
    }