上一篇文章(https://www.cnblogs.com/meowv/p/12909558.html)完善了專案中的程式碼，接入了Swagger。本篇主要使用Entity Framework Core完成對資料庫的訪問，以及使用Code-First的方式進行資料遷移，自動建立表結構。
資料訪問
在.EntityFrameworkCore專案中新增我們的資料訪問上下文物件MeowvBlogDbContext，繼承自 AbpDbContext<T>。然後重寫OnModelCreating方法。
OnModelCreating：定義EF Core 實體對映。先呼叫 base.OnModelCreating 讓 abp 框架為我們實現基礎對映，然後呼叫builder.Configure()擴充套件方法來配置應用程式的實體。當然也可以不用擴充套件，直接寫在裡面，這樣一大坨顯得不好看而已。
在abp框架中，可以使用 [ConnectionStringName] Attribute 為我們的DbContext配置連線字串名稱。先加上，然後再在appsettings.json中進行配置，因為之前整合了多個資料庫，所以這裡我們也配置多個連線字串，與之對應。
本專案預設採用MySql，你可以選擇任意你喜歡的。
//MeowvBlogDbContext.cs
using Microsoft.EntityFrameworkCore;
using Volo.Abp.Data;
using Volo.Abp.EntityFrameworkCore;
namespace Meowv.Blog.EntityFrameworkCore
{
[ConnectionStringName("MySql")]
public class MeowvBlogDbContext : AbpDbContext<MeowvBlogDbContext>
{
public MeowvBlogDbContext(DbContextOptions<MeowvBlogDbContext> options) : base(options)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Configure();
}
}
}
//appsettings.json
{
"ConnectionStrings": {
"Enable": "MySQL",
"MySql": "Server=localhost;User Id=root;Password=123456;Database=meowv_blog_tutorial",
"SqlServer": "",
"PostgreSql": "",
"Sqlite": ""
}
}
然後新建我們的擴充套件類MeowvBlogDbContextModelCreatingExtensions.cs和擴充套件方法Configure()。注意，擴充套件方法是靜態的，需加static
//MeowvBlogDbContextModelCreatingExtensions.cs
using Microsoft.EntityFrameworkCore;
using Volo.Abp;
namespace Meowv.Blog.EntityFrameworkCore
{
public static class MeowvBlogDbContextModelCreatingExtensions
{
public static void Configure(this ModelBuilder builder)
{
Check.NotNull(builder, nameof(builder));
...
}
}
}
完成上述操作後在我們的模組類MeowvBlogFrameworkCoreModule中將DbContext註冊到依賴注入，根據你配置的值使用不同的資料庫。在.Domain層建立配置檔案訪問類AppSettings.cs
//AppSettings.cs
using Microsoft.Extensions.Configuration;
using System.IO;
namespace Meowv.Blog.Domain.Configurations
{
/// <summary>
/// appsettings.json配置檔案資料讀取類
/// </summary>
public class AppSettings
{
/// <summary>
/// 配置檔案的根節點
/// </summary>
private static readonly IConfigurationRoot _config;
/// <summary>
/// Constructor
/// </summary>
static AppSettings()
{
// 載入appsettings.json，並構建IConfigurationRoot
var builder = new ConfigurationBuilder().SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", true, true);
_config = builder.Build();
}
/// <summary>
/// EnableDb
/// </summary>
public static string EnableDb => _config["ConnectionStrings:Enable"];
/// <summary>
/// ConnectionStrings
/// </summary>
public static string ConnectionStrings => _config.GetConnectionString(EnableDb);
}
}
獲取配置檔案內容比較容易，程式碼中有註釋也很容易理解。
值得一提的是，ABP會自動為DbContext中的實體建立預設倉儲. 需要在註冊的時使用options新增AddDefaultRepositories()。
預設情況下為每個實體建立一個倉儲，如果想要為其他實體也建立倉儲，可以將 includeAllEntities 設定為 true，然後就可以在服務中注入和使用 IRepository<TEntity> 或 IQueryableRepository<TEntity>
//MeowvBlogFrameworkCoreModule.cs
using Meowv.Blog.Domain;
using Meowv.Blog.Domain.Configurations;
using Microsoft.Extensions.DependencyInjection;
using Volo.Abp.EntityFrameworkCore;
using Volo.Abp.EntityFrameworkCore.MySQL;
using Volo.Abp.EntityFrameworkCore.PostgreSql;
using Volo.Abp.EntityFrameworkCore.Sqlite;
using Volo.Abp.EntityFrameworkCore.SqlServer;
using Volo.Abp.Modularity;
namespace Meowv.Blog.EntityFrameworkCore
{
[DependsOn(
typeof(MeowvBlogDomainModule),
typeof(AbpEntityFrameworkCoreModule),
typeof(AbpEntityFrameworkCoreMySQLModule),
typeof(AbpEntityFrameworkCoreSqlServerModule),
typeof(AbpEntityFrameworkCorePostgreSqlModule),
typeof(AbpEntityFrameworkCoreSqliteModule)
)]
public class MeowvBlogFrameworkCoreModule : AbpModule
{
public override void ConfigureServices(ServiceConfigurationContext context)
{
context.Services.AddAbpDbContext<MeowvBlogDbContext>(options =>
{
options.AddDefaultRepositories(includeAllEntities: true);
});
Configure<AbpDbContextOptions>(options =>
{
switch (AppSettings.EnableDb)
{
case "MySQL":
options.UseMySQL();
break;
case "SqlServer":
options.UseSqlServer();
break;
case "PostgreSql":
options.UsePostgreSql();
break;
case "Sqlite":
options.UseSqlite();
break;
default:
options.UseMySQL();
break;
}
});
}
}
}
現在可以來初步設計部落格所需表為：發表文章表(posts)、分類表(categories)、標籤表(tags)、文章對應標籤表(post_tags)、友情連結表(friendlinks)
在.Domain層編寫實體類，Post.cs、Category.cs、Tag.cs、PostTag.cs、FriendLink.cs。把主鍵設定為int型，直接繼承Entity
點選檢視程式碼
//Post.cs
using System;
using Volo.Abp.Domain.Entities;
namespace Meowv.Blog.Domain.Blog
{
/// <summary>
/// Post
/// </summary>
public class Post : Entity<int>
{
/// <summary>
/// 標題
/// </summary>
public string Title { get; set; }
/// <summary>
/// 作者
/// </summary>
public string Author { get; set; }
/// <summary>
/// 連結
/// </summary>
public string Url { get; set; }
/// <summary>
/// HTML
/// </summary>
public string Html { get; set; }
/// <summary>
/// Markdown
/// </summary>
public string Markdown { get; set; }
/// <summary>
/// 分類Id
/// </summary>
public int CategoryId { get; set; }
/// <summary>
/// 建立時間
/// </summary>
public DateTime CreationTime { get; set; }
}
}
//Category.cs
using Volo.Abp.Domain.Entities;
namespace Meowv.Blog.Domain.Blog
{
/// <summary>
/// Category
/// </summary>
public class Category : Entity<int>
{
/// <summary>
/// 分類名稱
/// </summary>
public string CategoryName { get; set; }
/// <summary>
/// 展示名稱
/// </summary>
public string DisplayName { get; set; }
}
}
//Tag.cs
using Volo.Abp.Domain.Entities;
namespace Meowv.Blog.Domain.Blog
{
/// <summary>
/// Tag
/// </summary>
public class Tag : Entity<int>
{
/// <summary>
/// 標籤名稱
/// </summary>
public string TagName { get; set; }
/// <summary>
/// 展示名稱
/// </summary>
public string DisplayName { get; set; }
}
}
//PostTag.cs
using Volo.Abp.Domain.Entities;
namespace Meowv.Blog.Domain.Blog
{
/// <summary>
/// PostTag
/// </summary>
public class PostTag : Entity<int>
{
/// <summary>
/// 文章Id
/// </summary>
public int PostId { get; set; }
/// <summary>
/// 標籤Id
/// </summary>
public int TagId { get; set; }
}
}
//FriendLink.cs
using Volo.Abp.Domain.Entities;
namespace Meowv.Blog.Domain.Blog
{
/// <summary>
/// FriendLink
/// </summary>
public class FriendLink : Entity<int>
{
/// <summary>
/// 標題
/// </summary>
public string Title { get; set; }
/// <summary>
/// 連結
/// </summary>
public string LinkUrl { get; set; }
}
}
建立好實體類後，在MeowvBlogDbContext新增DbSet屬性
//MeowvBlogDbContext.cs
...
[ConnectionStringName("MySql")]
public class MeowvBlogDbContext : AbpDbContext<MeowvBlogDbContext>
{
public DbSet<Post> Posts { get; set; }
public DbSet<Category> Categories { get; set; }
public DbSet<Tag> Tags { get; set; }
public DbSet<PostTag> PostTags { get; set; }
public DbSet<FriendLink> FriendLinks { get; set; }
...
}
...
在.Domain.Shared層新增全域性常量類MeowvBlogConsts.cs和表名常量類MeowvBlogDbConsts.cs，搞一個表字首的常量，我這裡寫的是meowv_，大家可以隨意。代表我們的表名都將以meowv_開頭。然後在MeowvBlogDbConsts中將表名稱定義好。
//MeowvBlogConsts.cs
namespace Meowv.Blog.Domain.Shared
{
/// <summary>
/// 全域性常量
/// </summary>
public class MeowvBlogConsts
{
/// <summary>
/// 資料庫表字首
/// </summary>
public const string DbTablePrefix = "meowv_";
}
}
//MeowvBlogDbConsts.cs
namespace Meowv.Blog.Domain.Shared
{
public class MeowvBlogDbConsts
{
public static class DbTableName
{
public const string Posts = "Posts";
public const string Categories = "Categories";
public const string Tags = "Tags";
public const string PostTags = "Post_Tags";
public const string Friendlinks = "Friendlinks";
}
}
}
在Configure()方法中配置表模型，包括表名、欄位型別和長度等資訊。對於下面程式碼不是很明白的可以看看微軟的自定義 Code First 約定：https://docs.microsoft.com/zh-cn/ef/ef6/modeling/code-first/conventions/custom
//MeowvBlogDbContextModelCreatingExtensions.cs
using Meowv.Blog.Domain.Blog;
using Meowv.Blog.Domain.Shared;
using Microsoft.EntityFrameworkCore;
using Volo.Abp;
using static Meowv.Blog.Domain.Shared.MeowvBlogDbConsts;
namespace Meowv.Blog.EntityFrameworkCore
{
public static class MeowvBlogDbContextModelCreatingExtensions
{
public static void Configure(this ModelBuilder builder)
{
Check.NotNull(builder, nameof(builder));
builder.Entity<Post>(b =>
{
b.ToTable(MeowvBlogConsts.DbTablePrefix + DbTableName.Posts);
b.HasKey(x => x.Id);
b.Property(x => x.Title).HasMaxLength(200).IsRequired();
b.Property(x => x.Author).HasMaxLength(10);
b.Property(x => x.Url).HasMaxLength(100).IsRequired();
b.Property(x => x.Html).HasColumnType("longtext").IsRequired();
b.Property(x => x.Markdown).HasColumnType("longtext").IsRequired();
b.Property(x => x.CategoryId).HasColumnType("int");
b.Property(x => x.CreationTime).HasColumnType("datetime");
});
builder.Entity<Category>(b =>
{
b.ToTable(MeowvBlogConsts.DbTablePrefix + DbTableName.Categories);
b.HasKey(x => x.Id);
b.Property(x => x.CategoryName).HasMaxLength(50).IsRequired();
b.Property(x => x.DisplayName).HasMaxLength(50).IsRequired();
});
builder.Entity<Tag>(b =>
{
b.ToTable(MeowvBlogConsts.DbTablePrefix + DbTableName.Tags);
b.HasKey(x => x.Id);
b.Property(x => x.TagName).HasMaxLength(50).IsRequired();
b.Property(x => x.DisplayName).HasMaxLength(50).IsRequired();
});
builder.Entity<PostTag>(b =>
{
b.ToTable(MeowvBlogConsts.DbTablePrefix + DbTableName.PostTags);
b.HasKey(x => x.Id);
b.Property(x => x.PostId).HasColumnType("int").IsRequired();
b.Property(x => x.TagId).HasColumnType("int").IsRequired();
});
builder.Entity<FriendLink>(b =>
{
b.ToTable(MeowvBlogConsts.DbTablePrefix + DbTableName.Friendlinks);
b.HasKey(x => x.Id);
b.Property(x => x.Title).HasMaxLength(20).IsRequired();
b.Property(x => x.LinkUrl).HasMaxLength(100).IsRequired();
});
}
}
}
此時專案層級目錄如下
程式碼優先
在.EntityFrameworkCore.DbMigrations中新建模組類MeowvBlogEntityFrameworkCoreDbMigrationsModule.cs、資料遷移上下文訪問物件MeowvBlogMigrationsDbContext.cs和一個Design Time Db Factory類MeowvBlogMigrationsDbContextFactory.cs
模組類依賴MeowvBlogFrameworkCoreModule模組和AbpModule。並在ConfigureServices方法中新增上下文的依賴注入。
//MeowvBlogEntityFrameworkCoreDbMigrationsModule.cs
using Microsoft.Extensions.DependencyInjection;
using Volo.Abp.Modularity;
namespace Meowv.Blog.EntityFrameworkCore.DbMigrations.EntityFrameworkCore
{
[DependsOn(
typeof(MeowvBlogFrameworkCoreModule)
)]
public class MeowvBlogEntityFrameworkCoreDbMigrationsModule : AbpModule
{
public override void ConfigureServices(ServiceConfigurationContext context)
{
context.Services.AddAbpDbContext<MeowvBlogMigrationsDbContext>();
}
}
}
MeowvBlogMigrationsDbContext和MeowvBlogDbContext沒什麼大的區別
//MeowvBlogMigrationsDbContext.cs
using Microsoft.EntityFrameworkCore;
using Volo.Abp.EntityFrameworkCore;
namespace Meowv.Blog.EntityFrameworkCore.DbMigrations.EntityFrameworkCore
{
public class MeowvBlogMigrationsDbContext : AbpDbContext<MeowvBlogMigrationsDbContext>
{
public MeowvBlogMigrationsDbContext(DbContextOptions<MeowvBlogMigrationsDbContext> options) : base(options)
{
}
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
builder.Configure();
}
}
}
MeowvBlogMigrationsDbContextFactory類主要是用來使用Code-First命令的(Add-Migration 和 Update-Database ...)
需要注意的地方，我們在這裡要單獨設定配置檔案的連線字串，將.HttpApi.Hosting層的appsettings.json複製一份到.EntityFrameworkCore.DbMigrations，你用了什麼資料庫就配置什麼資料庫的連線字串。
//appsettings.json
{
"ConnectionStrings": {
"Default": "Server=localhost;User Id=root;Password=123456;Database=meowv_blog"
}
}
//MeowvBlogMigrationsDbContextFactory.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;
using Microsoft.Extensions.Configuration;
using System.IO;
namespace Meowv.Blog.EntityFrameworkCore.DbMigrations.EntityFrameworkCore
{
public class MeowvBlogMigrationsDbContextFactory : IDesignTimeDbContextFactory<MeowvBlogMigrationsDbContext>
{
public MeowvBlogMigrationsDbContext CreateDbContext(string[] args)
{
var configuration = BuildConfiguration();
var builder = new DbContextOptionsBuilder<MeowvBlogMigrationsDbContext>()
.UseMySql(configuration.GetConnectionString("Default"));
return new MeowvBlogMigrationsDbContext(builder.Options);
}
private static IConfigurationRoot BuildConfiguration()
{
var builder = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
return builder.Build();
}
}
}
到這裡差不多就結束了，預設資料庫meowv_blog_tutorial是不存在的，先去建立一個空的資料庫。
然後在Visual Studio中開啟程式包管理控制檯，將.EntityFrameworkCore.DbMigrations設為啟動專案。
鍵入命令：Add-Migration Initial,會發現報錯啦，錯誤資訊如下：
Add-Migration : 無法將“Add-Migration”項識別為 cmdlet、函式、指令碼檔案或可執行程式的名稱。請檢查名稱的拼寫，如果包括路徑，請確保路徑正確，然後再試一次。
所在位置 行:1 字元: 1
+ Add-Migration Initial
+ ~~~~~~~~~~~~~
+ CategoryInfo : ObjectNotFound: (Add-Migration:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
這是因為我們少新增了一個包，要使用程式碼優先方式遷移資料，必須新增，Microsoft.EntityFrameworkCore.Tools。
緊接著直接用命令安裝Install-Package Microsoft.EntityFrameworkCore.Tools包，再試一遍
可以看到已經成功，並且生成了一個Migrations資料夾和對應的資料遷移檔案
最後輸入更新命令：Update-Database，然後開啟資料瞅瞅。
完美，成功建立了資料庫表，而且命名也是我們想要的，欄位型別也是ok的。__efmigrationshistory表是用來記錄遷移歷史的，這個可以不用管。當我們後續如果想要修改新增表欄位，新增表的時候，都可以使用這種方式來完成。
解決方案層級目錄圖，供參考
本篇使用Entity Framework Core完成資料訪問和程式碼優先的方式建立資料庫表，你學會了嗎？???