asp.net core EF code first

以連接mysql資料庫為例

一 安裝組件

Microsoft.EntityFrameworkCore

Microsoft.EntityFrameworkCore.Relational

Microsoft.EntityFrameworkCore.Tools

MySqlConnector

Pomelo.EntityFrameworkCore.MySql

二 新增MySQLDbContext,繼承自DbContext,並新增一個資料庫表實體Article

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

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

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

        /// <summary>
        /// 創建時間
        /// </summary>
        public DateTime CreatedDT { get; set; }

        /// <summary>
        /// 修改時間
        /// </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配置資料庫連接字元串,併在Startup.cs中添加服務

 Startup.cs:

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

　註:字元串連接名稱"MySQL"與appsettings中配置的名稱對應.

四 code first方式創建資料庫

1.程式包管理控制台PM命令

1 remove-migrations
2 add-migrations my-gration
3 update-database

2.donet命令行

1 dotnet ef migrations remove
2 dotnet ef migrations add my-gration
3 dotnet ef database update

3.代碼內執行創建資料庫的代碼(EnsureCreated)

新增DbContextExtension擴展類EnsureCreatedDB擴展方法:

1 public static IWebHost EnsureCreatedDB<TContext>(this IWebHost host) where TContext : DbContext
2 {
3     using (var scope = host.Services.CreateScope())
4     {
5     　　var context = scope.ServiceProvider.GetService<TContext>();
6     　　context.Database.EnsureCreated();
7     }
8     return host;
9 }

在Program.cs中調用該擴展方法:

1 public static void Main(string[] args)
2 {
3     CreateWebHostBuilder(args).Build()
4     .EnsureCreatedDB<MySQLDbContext>()  //調用擴展方法
5     .Run();
6 }

五 使用EF進行增刪改查

 1     [ApiController]
 2     [Route("api-hd/article")]
 3     public class ArticleController : ControllerBase
 4     {
 5         private MySQLDbContext _dbContext;
 6 
 7         public ArticleController(MySQLDbContext dbContext)
 8         {
 9             _dbContext = dbContext;
10         }
11 
12         /// <summary>
13         /// 新增文章
14         /// </summary>
15         /// <param name="title"></param>
16         /// <param name="content"></param>
17         /// <returns></returns>
18         [AllowAnonymous]
19         [HttpPost]
20         [Route("")]
21         public async Task<bool> Add(string title, string content)
22         {
23             var newArticle = new Article()
24             {
25                 Id = Guid.NewGuid().ToString(),
26                 Title = title,
27                 Content = content,
28                 CreatedDT = DateTime.Now,
29                 ModifiedDT = DateTime.Now,
30             };
31             await _dbContext.AddAsync(newArticle);
32             await _dbContext.SaveChangesAsync();
33             return true;
34         }
35 
36         /// <summary>
37         /// 根據id查詢文章
38         /// </summary>
39         /// <param name="id"></param>
40         /// <returns></returns>
41         [AllowAnonymous]
42         [HttpGet]
43         [Route("{id}")]
44         public async Task<Article> GetById(string id)
45         {
46             var data = await _dbContext.ArticleSets.FindAsync(id);
47             return data;
48         }
49 
50         /// <summary>
51         /// 更新文章標題
52         /// </summary>
53         /// <param name="id"></param>
54         /// <param name="title"></param>
55         /// <returns></returns>
56         [AllowAnonymous]
57         [HttpPut]
58         [Route("")]
59         public async Task<bool> Update(string id, string title)
60         {
61             var existArticle = await _dbContext.ArticleSets.FindAsync(id);
62             if (existArticle == null)
63             {
64                 return false;
65             }
66 
67             existArticle.Title = title;
68             //_dbContext.Update(existArticle);
69             await _dbContext.SaveChangesAsync();
70             return true;
71         }
72 
73         /// <summary>
74         /// 根據id刪除文章
75         /// </summary>
76         /// <param name="id"></param>
77         /// <returns></returns>
78         [AllowAnonymous]
79         [HttpDelete]
80         [Route("{id}")]
81         public async Task<bool> Delete(string id)
82         {
83             var existArticle = await _dbContext.ArticleSets.FindAsync(id);
84             if (existArticle == null)
85             {
86                 return false;
87             }
88 
89             _dbContext.Remove(existArticle);
90             await _dbContext.SaveChangesAsync();
91             return true;
92         }
93         
94     }