009.Working with SQL Server LocalDB --【在sql server localdb 上操作数据】

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Working with SQL Server LocalDB

在sql server localdb 上操作数据

2017-3-7 2 分钟阅读时长

本文内容

1.SQL Server Express LocalDB

SQL Server Express LocalDB sql server 的一个简化免费版本

2.Seed the database

初始化数据库的初始表数据

By Rick Anderson

The MvcMovieContext object handles the task of connecting to the database and mapping Movie objects to database records.

MvcMovieContext 对象处理了链接数据库与映射Movie 对象到表记录的任务.

The database context is registered with the Dependency Injection container in the ConfigureServices method in the Startup.cs file:

DB上下文在 Startup.cs 文件的ConfigureServices 方法中被注册到了DI容器中:

 public void ConfigureServices(IServiceCollection services)

 {

     // Add framework services.

     services.AddMvc();

     services.AddDbContext<MvcMovieContext>(options =>

             options.UseSqlServer(Configuration.GetConnectionString("MvcMovieContext")));

 }

C# code

The ASP.NET Core Configuration system reads the ConnectionString.

Asp.net core 的配置系统读取了ConnectionString 的配置的值。

For local development, it gets the connection string from the appsettings.json file:

对于本地开发，它从 appsettings.json 文件获取链接字符串的值：

 "ConnectionStrings": {

   "MvcMovieContext": "Server=(localdb)\\mssqllocaldb;Database=MvcMovieContext-20613a4b-deb5-4145-b6cc-a5fd19afda13;Trusted_Connection=True;MultipleActiveResultSets=true"

 }

JSON Code

When you deploy the app to a test or production server, you can use an environment variable or another approach to set the connection string to a real SQL Server.

当你将应用部署到一个测试或生产服务器，你可以使用环境变量或其它的方法来设置一个真实的db链接字符串的值。

See Configuration for more information.

查看Configuration 获取更多信息。

SQL Server Express LocalDB

（一个简化的免费的轻量的sql server 版本）

LocalDB is a lightweight version of the SQL Server Express Database Engine that is targeted for program development.

LocalDB 是 SQL Server Express Database Engine 的一个轻量版本，目的是本地的程序开发。

LocalDB starts on demand and runs in user mode, so there is no complex configuration.

LocalDB 以用户模式直接开始查询即可，因此没有复杂的配置。

By default, LocalDB database creates "*.mdf" files in the C:/Users/<user> directory.

默认情况下，LocalDB 会在 C:/Users/<user> 文件夹下创建"*.mdf" 数据库文件。

From the View menu, open SQL Server Object Explorer (SSOX).

从 View 菜单，打开 SQL Server Object Explorer ：

Right click on the Movie table > View Designer

右击 Movie 表，点击 > View Designer 菜单

Note the key icon next to ID. By default, EF will make a property named ID the primary key.

注意PK图标在ID 字段旁边，EF默认会使用ID做为一个PK。

Right click on the Movie table > View Data

右击 Movie 表，选择 > View Data 菜单

Seed the database

向数据库初始化值

Create a new class named SeedData in the Models folder. Replace the generated code with the following:

在 Models 文件夹下新建一个名为SeedData 类，用下面的代码替换掉自动生成的代码：

 using Microsoft.EntityFrameworkCore;

 using Microsoft.Extensions.DependencyInjection;

 using System;

 using System.Linq;

 namespace MvcMovie.Models

 {

     public static class SeedData

     {

         public static void Initialize(IServiceProvider serviceProvider)

         {

             using (var context = new MvcMovieContext(

                 serviceProvider.GetRequiredService<DbContextOptions<MvcMovieContext>>()))

             {

                 // Look for any movies.

                 if (context.Movie.Any())

                 {

                     return;   // DB has been seeded

                 }

                 context.Movie.AddRange(

                      new Movie

                      {

                          Title = "When Harry Met Sally",

                          ReleaseDate = DateTime.Parse("1989-1-11"),

                          Genre = "Romantic Comedy",

                          Price = 7.99M

                      },

                      new Movie

                      {

                          Title = "Ghostbusters ",

                          ReleaseDate = DateTime.Parse("1984-3-13"),

                          Genre = "Comedy",

                          Price = 8.99M

                      },

                      new Movie

                      {

                          Title = "Ghostbusters 2",

                          ReleaseDate = DateTime.Parse("1986-2-23"),

                          Genre = "Comedy",

                          Price = 9.99M

                      },

                    new Movie

                    {

                        Title = "Rio Bravo",

                        ReleaseDate = DateTime.Parse("1959-4-15"),

                        Genre = "Western",

                        Price = 3.99M

                    }

                 );

                 context.SaveChanges();

             }

         }

     }

 }

C# Code

If there are any movies in the DB, the seed initializer returns and no movies are added.

如果数据库中有数据记录，就会直接返回，如果没有就会添加这些初始数据。

 if (context.Movie.Any())

 {

     return;   // DB has been seeded.

 }

C# Code

Add the seed initializer to the end of the Configure method in the Startup.cs file:

把数据初始化类添加到 Startup.cs 文件的Configure 方法的最后一行：

             app.UseStaticFiles();

             app.UseMvc(routes =>

             {

                 routes.MapRoute(

                     name: "default",

                     template: "{controller=Home}/{action=Index}/{id?}");

             });

             SeedData.Initialize(app.ApplicationServices);

         }

     }

 }

C# Code

Test the app

测试应用