使用EF Core的Code First模式,通過遷移來同步資料庫與模型.

環境: JetBrains Rider Window10 .NET5

一. 建立專案

1. 使用JetBrains Rider建立一個web api專案

2. 使用NuGet安裝依賴包

   • Microsoft.EntityFrameworkCore
   • Microsoft.EntityFrameworkCore.Tools
   • Microsoft.EntityFrameworkCore.SqlServer 此依賴包根據使用的資料庫安裝相應的包, 這裡使用的是SQL Server

3. 建立資料庫上下文

   • 在專案中建立一個Data資料夾，建立一個類TestDBContext

     using Microsoft.EntityFrameworkCore;
     
     namespace Test.Data
     {
         public class TestDBContext : DbContext
         {
             public TestDBContext(DbContextOptions<TestDBContext> options) : base(options){}
         }
     }
     

4. 建立資料模型

   • 在專案中建立一個Models資料夾，建立部門類Department, 員工類Personnel

     using System.Collections.Generic;
     using System.ComponentModel.DataAnnotations;
     using System.ComponentModel.DataAnnotations.Schema;
     
     namespace Test.Models
     {
         /// <summary>
         /// 部門類
         /// </summary>
         public class Department
         {
             [Key] // 主鍵
             [DatabaseGenerated(DatabaseGeneratedOption.Identity)]  //設定自增
             public int Id { get; set; }
             
             [Required]
             [MaxLength(50)]
             public string Name { get; set; }
     
             // Department 與 Personnel 一對多
             public ICollection<Personnel> Personnels { get; set; } = new List<Personnel>();
         }
     }
      
     

     using System.ComponentModel.DataAnnotations;
     using System.ComponentModel.DataAnnotations.Schema;
     
     namespace Test.Models
     {
         /// <summary>
         /// 員工類
         /// </summary>
         public class Personnel
         {
             [Key]
             [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
             public int Id { get; set; }
             
             [Required]
             [MaxLength(50)]
             public string Name { get; set; }
             
             public int Age { get; set; }
             
             [ForeignKey("Department")] // 外來鍵
             public int DepartmentId { get; set; }
         }
     }
      
     

5. 在之前建立的資料庫上下文TestDBContext中註冊資料模型

   using Microsoft.EntityFrameworkCore;
   using Test.Models;
   
   namespace Test.Data
   {
       public class TestDBContext : DbContext
       {
           public TestDBContext(DbContextOptions<TestDBContext> options) : base(options){}
           
           // 註冊資料模型
           // 模型集的名稱與對應的表名相同
           public DbSet<Department> Departments { get; set; }
           public DbSet<Personnel> Personnels { get; set; }
       }
   }
   

6. 在appsettings.json中新增資料庫連線字串

   {
     "Logging": {
       "LogLevel": {
         "Default": "Information",
         "Microsoft": "Warning",
         "Microsoft.Hosting.Lifetime": "Information"
       }
     },
     "AllowedHosts": "*",
     "connectionStrings": {
       "SqlServerContext": "Data Source=伺服器名;Initial Catalog=資料庫名; User Id=使用者名稱;Password=密碼"
     }
   }
   

7. 在Startup中註冊資料庫上下文TestDBContext

   using Microsoft.AspNetCore.Builder;
   using Microsoft.AspNetCore.Hosting;
   using Microsoft.EntityFrameworkCore;
   using Microsoft.Extensions.Configuration;
   using Microsoft.Extensions.DependencyInjection;
   using Microsoft.Extensions.Hosting;
   using Microsoft.OpenApi.Models;
   using Test.Data;
   
   namespace Test
   {
       public class Startup
       {
           // 注入 IConfiguration:有關配置檔案最底層的一個介面型別
           public Startup(IConfiguration configuration)
           {
               _Configuration = configuration;
           }
   
           private IConfiguration _Configuration { get; }
   
           // This method gets called by the runtime. Use this method to add services to the container.
           public void ConfigureServices(IServiceCollection services)
           {
               services.AddControllers();
               services.AddSwaggerGen(c => { c.SwaggerDoc("v1", 
                   new OpenApiInfo {Title = "Test", Version = "v1"}); });
               // 註冊資料庫上下文
               // _Configuration["connectionStrings:SqlServerContext"] 獲取資料庫連線字串
               services.AddDbContext<TestDBContext>(option
                   => option.UseSqlServer(_Configuration["connectionStrings:SqlServerContext"]));
           }
   
           // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
           public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
           {
               if (env.IsDevelopment())
               {
                   app.UseDeveloperExceptionPage();
                   app.UseSwagger();
                   app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "Test v1"));
               }
   
               app.UseHttpsRedirection();
   
               app.UseRouting();
   
               app.UseAuthorization();
   
               app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
           }
       }
   }
   

8. 遷移

   • 開啟Terminal視窗或者cmd進入專案根目錄執行遷移命令: dotnet ef migrations add 本次遷移的名稱
   • 如果未安裝dotnet ef, 會無法執行
   • 安裝全域性dotnet ef
   • 再次執行遷移命令
   • 遷移成功後, 專案中有一個Migrations目錄, 儲存著每次遷移的記錄

9. 更新資料庫

   • 執行dotnet ef database update
   • 資料庫更新成功, 資料庫就已經建立好了
   • 當資料模型發生改變時, 只用再次執行遷移/更新資料庫

二. 新增初始資料

1. 在資料上下文TestDBContext中重寫OnModelCreating方法

   using System.Collections.Generic;
   using Microsoft.EntityFrameworkCore;
   using Test.Models;
   
   namespace Test.Data
   {
       public class TestDBContext : DbContext
       {
           public TestDBContext(DbContextOptions<TestDBContext> options) : base(options){}
           
           // 註冊資料模型
           // 模型集的名稱與對應的表名相同
           public DbSet<Department> Departments { get; set; }
           public DbSet<Personnel> Personnels { get; set; }
   
           // 控制資料庫和模型對映, 通過它可以自定義對映關係
           protected override void OnModelCreating(ModelBuilder modelBuilder)
           {
               modelBuilder.Entity<Department>()
                   .HasData(new List<Department>()
                   {
                       new Department() {Id = 1, Name = "人力資源部"},
                       new Department() {Id = 2, Name = "技術部"}
                   });
               modelBuilder.Entity<Personnel>()
                   .HasData(new List<Personnel>()
                   {
                       new Personnel() {Id = 1, Name = "張三", Age = 23, DepartmentId = 2},
                       new Personnel() {Id = 2, Name = "李四", Age = 20, DepartmentId = 1},
                       new Personnel() {Id = 3, Name = "王五", Age = 25, DepartmentId = 2}
                   });
               base.OnModelCreating(modelBuilder);
           }
       }
   }
   

2. 遷移, 更新資料庫