Asp.net core 通过Models 生成数据库的方法

    其实Getting Started当中有着详细的说明,https://docs.efproject.net/en/latest/platforms/aspnetcore/new-db.html。但是有网友问道,就说一下好了。

  1. 新建项目,Asp.net core,选择不适用身份验证。
  2. 添加项目引用。这里还是使用postgreSql。

    在Nuget 控制台中输入命令:

    Install-Package Npgsql.EntityFrameworkCore.PostgreSQL

    Install-Package Microsoft.EntityFrameworkCore.Tools –Pre

    添加这两个依赖

    然后手动在Tools 节点中加上 "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",

    这里发现Tools –Pre就可以正常使用nuget安装,昨天直接获取版本安装失败,看来还是nuget同步问题。

  3. 创建Model类 Blogs,Post和DBContext

    using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Threading.Tasks;

     

    namespace PostgreSqlDemo2.Models

    {

    public class Blog

    {

    public int BlogId { get; set; }

    public string Url { get; set; }

     

    public List<Post> Posts { get; set; }

    }

    }

     

    using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Threading.Tasks;

     

    namespace PostgreSqlDemo2.Models

    {

    public class Post

    {

    public int PostId { get; set; }

    public string Title { get; set; }

    public string Content { get; set; }

     

    public int BlogId { get; set; }

    public Blog Blog { get; set; }

    }

    }

     

    using Microsoft.EntityFrameworkCore;

    using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Threading.Tasks;

     

    namespace PostgreSqlDemo2.Models

    {

    public class BloggingContext : DbContext

    {

    public BloggingContext(DbContextOptions<BloggingContext> options)

    : base(options)

    { }

     

    public DbSet<Blog> Blogs { get; set; }

    public DbSet<Post> Posts { get; set; }

    }

     

    }

  4. 在Startup.cs类中注册DBContext

     

public void ConfigureServices(IServiceCollection services)

{

// Add framework services.

services.AddApplicationInsightsTelemetry(Configuration);

 

services.AddDbContext<BloggingContext>(options =>

options.UseNpgsql(Configuration.GetConnectionString("DefaultConnection")));

 

services.AddMvc();

}

  1. Appsetting.json中增加连接字符串

    "ConnectionStrings": {

    "DefaultConnection": "User ID=test;Password=test;Host=192.168.1.6;Database=testdb;Pooling=true;"

    },

  2. 创建 Migration

    这里要说一下,Migration是ef框架设计的工具,能够用来生成一些框架类。在vs2015中,可以在Nuget控制台中使用Add-Migration,linux或者cmd中,可以使用dotnet ef migration命令,具体请自行学习。

    言归正传,我们开始生成类,在Nuget控制台中输入命令:

    Add-Migration MyFirstMigration

    等待结束,笔者这里会报一个"无法识别的转义序列"的错误,但是不影响使用,笔者已经在apsnet上报了issue。

    然后我们会看到,项目结构中增加了一个文件夹及几个文件如下:

    Asp.net core 通过Models 生成数据库的方法_第1张图片

    查看代码:

    using System;

    using System.Collections.Generic;

    using Microsoft.EntityFrameworkCore.Migrations;

     

    namespace PostgreSqlDemo2.Migrations

    {

    public partial class MyFirstMigration : Migration

    {

    protected override void Up(MigrationBuilder migrationBuilder)

    {

    migrationBuilder.CreateTable(

    name: "Blogs",

    columns: table => new

    {

    BlogId = table.Column<int>(nullable: false)

    .Annotation("Npgsql:ValueGeneratedOnAdd", true),

    Url = table.Column<string>(nullable: true)

    },

    constraints: table =>

    {

    table.PrimaryKey("PK_Blogs", x => x.BlogId);

    });

     

    migrationBuilder.CreateTable(

    name: "Posts",

    columns: table => new

    {

    PostId = table.Column<int>(nullable: false)

    .Annotation("Npgsql:ValueGeneratedOnAdd", true),

    BlogId = table.Column<int>(nullable: false),

    Content = table.Column<string>(nullable: true),

    Title = table.Column<string>(nullable: true)

    },

    constraints: table =>

    {

    table.PrimaryKey("PK_Posts", x => x.PostId);

    table.ForeignKey(

    name: "FK_Posts_Blogs_BlogId",

    column: x => x.BlogId,

    principalTable: "Blogs",

    principalColumn: "BlogId",

    onDelete: ReferentialAction.Cascade);

    });

     

    migrationBuilder.CreateIndex(

    name: "IX_Posts_BlogId",

    table: "Posts",

    column: "BlogId");

    }

     

    protected override void Down(MigrationBuilder migrationBuilder)

    {

    migrationBuilder.DropTable(

    name: "Posts");

     

    migrationBuilder.DropTable(

    name: "Blogs");

    }

    }

    }

    Design.cs

    using System;

    using Microsoft.EntityFrameworkCore;

    using Microsoft.EntityFrameworkCore.Infrastructure;

    using Microsoft.EntityFrameworkCore.Metadata;

    using Microsoft.EntityFrameworkCore.Migrations;

    using PostgreSqlDemo2.Models;

     

    namespace PostgreSqlDemo2.Migrations

    {

    [DbContext(typeof(BloggingContext))]

    [Migration("20160713011245_MyFirstMigration")]

    partial class MyFirstMigration

    {

    protected override void BuildTargetModel(ModelBuilder modelBuilder)

    {

    modelBuilder

    .HasAnnotation("ProductVersion", "1.0.0-rtm-21431");

     

    modelBuilder.Entity("PostgreSqlDemo2.Models.Blog", b =>

    {

    b.Property<int>("BlogId")

    .ValueGeneratedOnAdd();

     

    b.Property<string>("Url");

     

    b.HasKey("BlogId");

     

    b.ToTable("Blogs");

    });

     

    modelBuilder.Entity("PostgreSqlDemo2.Models.Post", b =>

    {

    b.Property<int>("PostId")

    .ValueGeneratedOnAdd();

     

    b.Property<int>("BlogId");

     

    b.Property<string>("Content");

     

    b.Property<string>("Title");

     

    b.HasKey("PostId");

     

    b.HasIndex("BlogId");

     

    b.ToTable("Posts");

    });

     

    modelBuilder.Entity("PostgreSqlDemo2.Models.Post", b =>

    {

    b.HasOne("PostgreSqlDemo2.Models.Blog", "Blog")

    .WithMany("Posts")

    .HasForeignKey("BlogId")

    .OnDelete(DeleteBehavior.Cascade);

    });

    }

    }

    }

     

    using System;

    using Microsoft.EntityFrameworkCore;

    using Microsoft.EntityFrameworkCore.Infrastructure;

    using Microsoft.EntityFrameworkCore.Metadata;

    using Microsoft.EntityFrameworkCore.Migrations;

    using PostgreSqlDemo2.Models;

     

    namespace PostgreSqlDemo2.Migrations

    {

    [DbContext(typeof(BloggingContext))]

    partial class BloggingContextModelSnapshot : ModelSnapshot

    {

    protected override void BuildModel(ModelBuilder modelBuilder)

    {

    modelBuilder

    .HasAnnotation("ProductVersion", "1.0.0-rtm-21431");

     

    modelBuilder.Entity("PostgreSqlDemo2.Models.Blog", b =>

    {

    b.Property<int>("BlogId")

    .ValueGeneratedOnAdd();

     

    b.Property<string>("Url");

     

    b.HasKey("BlogId");

     

    b.ToTable("Blogs");

    });

     

    modelBuilder.Entity("PostgreSqlDemo2.Models.Post", b =>

    {

    b.Property<int>("PostId")

    .ValueGeneratedOnAdd();

     

    b.Property<int>("BlogId");

     

    b.Property<string>("Content");

     

    b.Property<string>("Title");

     

    b.HasKey("PostId");

     

    b.HasIndex("BlogId");

     

    b.ToTable("Posts");

    });

     

    modelBuilder.Entity("PostgreSqlDemo2.Models.Post", b =>

    {

    b.HasOne("PostgreSqlDemo2.Models.Blog", "Blog")

    .WithMany("Posts")

    .HasForeignKey("BlogId")

    .OnDelete(DeleteBehavior.Cascade);

    });

    }

    }

    }

     

    上面代码都是自动生成的,生成依据就是你的Models中的实体类文件。

     

  3. 创建数据库

    虽然上面生成了数据库架构的代码,但是还没有更新到数据库中去。需要执行:

    Update-Database

    如果显示Done.

    则表示更新数据库成功。可以看看数据库中已经自动根据model实体创建了对应的数据表。

  4. 剩下的工作就和前文一样了,不在细说。

总结:

    记住几个命令 "Add-Migration MyFirstMigration","Update-Database"。注意执行时要保证代码能够正常编译,并且已经完成数据库的配置。如果数据库结构改了,可以修改Models下对应的实体类,然后删除Migration文件夹下的文件,然后从新执行这两个命令。笔者这里使用PostgreSQL的时候,报错了,提示Blogs表已存在,应该是issue,只能自行更新了。

转载于:https://www.cnblogs.com/lanwilliam/p/5666143.html

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