本节介绍数据库上下文
1、打开/Data/RazorPagesMovieContent.cs 、Startup.cs文件：
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Threading.Tasks; 5 using Microsoft.EntityFrameworkCore; 6 using RazorPagesMovie.Models; 7 8 namespace RazorPagesMovie.Data 9 { 10 public class RazorPagesMovieContext : DbContext 11 { 12 public RazorPagesMovieContext (DbContextOptions<RazorPagesMovieContext> options) 13 : base(options) 14 { 15 } 16 17 public DbSet<RazorPagesMovie.Models.Movie> Movie { get; set; } 18 } 19 }
RazorPagesMovieContent对象负责连接到数据库，并将Movie对象映射到数据库中的记录。在Start.cs文件中，ConfigureServices方法中向依赖关系注入（Dependency Injection）容器中注册数据库上下文，第30行：
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Threading.Tasks; 5 using Microsoft.AspNetCore.Builder; 6 using Microsoft.AspNetCore.Hosting; 7 using Microsoft.AspNetCore.HttpsPolicy; 8 using Microsoft.Extensions.Configuration; 9 using Microsoft.Extensions.DependencyInjection; 10 using Microsoft.Extensions.Hosting; 11 using Microsoft.EntityFrameworkCore; 12 using RazorPagesMovie.Data; 13 14 namespace RazorPagesMovie 15 { 16 public class Startup 17 { 18 public Startup(IConfiguration configuration) 19 { 20 Configuration = configuration; 21 } 22 23 public IConfiguration Configuration { get; } 24 25 // This method gets called by the runtime. Use this method to add services to the container. 26 public void ConfigureServices(IServiceCollection services) 27 { 28 services.AddRazorPages(); 29 30 services.AddDbContext<RazorPagesMovieContext>(options => 31 options.UseSqlServer(Configuration.GetConnectionString("RazorPagesMovieContext"))); 32 } 33 34 // This method gets called by the runtime. Use this method to configure the HTTP request pipeline. 35 public void Configure(IApplicationBuilder app, IWebHostEnvironment env) 36 { 37 if (env.IsDevelopment()) 38 { 39 app.UseDeveloperExceptionPage(); 40 } 41 else 42 { 43 app.UseExceptionHandler("/Error"); 44 // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts. 45 app.UseHsts(); 46 } 47 48 app.UseHttpsRedirection(); 49 app.UseStaticFiles(); 50 51 app.UseRouting(); 52 53 app.UseAuthorization(); 54 55 app.UseEndpoints(endpoints => 56 { 57 endpoints.MapRazorPages(); 58 }); 59 } 60 } 61 }
ASP.NET Core 配置系统会从appsettings.json文件中读取数据库连接字符串ConnectionString：
1 { 2 "Logging": { 3 "LogLevel": { 4 "Default": "Information", 5 "Microsoft": "Warning", 6 "Microsoft.Hosting.Lifetime": "Information" 7 } 8 }, 9 "AllowedHosts": "*", 10 "ConnectionStrings": { 11 "RazorPagesMovieContext": "Server=(localdb)\\mssqllocaldb;Database=RazorPagesMovieContext-6047c874-bb75-49ef-b998-62db7c5cbaf4;Trusted_Connection=True;MultipleActiveResultSets=true" 12 } 13 }
其中，Server表示服务器，这里是localdb\\mssqllocaldb；Database表示数据库名称，是一个系统自动生成的，数据库名可以是任意的。在将程序部署到测试或者生产服务器时，可以使用环境变量将连接字符串设置为实际的数据库服务器。以后再详细介绍。
2、SQL Server Express LocalDB
localdb，是轻型版的数据库引擎。按需启动。默认情况下，它将在c:\用户\你的用户名\目录下创建*.mdf和*_log.ldf文件。我这里生成的如下：
选择“视图”>"SQL Server 对象资源管理器"，在对象资源管理中我们可以看到刚才生成的数据库和表：
在dbo.Movie表上右键，选择“视图设计器”，可以查看表格结构以及对应的TSQL和表上其他的对象：
在dbo.Movie表上右键，选择“查看数据”，可以查看我们新增的电影记录：
3、设定数据库种子（Seed the database）
1 using Microsoft.EntityFrameworkCore; 2 using Microsoft.Extensions.DependencyInjection; 3 using RazorPagesMovie.Data; 4 using System; 5 using System.Linq; 6 7 namespace RazorPagesMovie.Models 8 { 9 public static class SeedData 10 { 11 public static void Initialize(IServiceProvider serviceProvider) 12 { 13 using (var context = new RazorPagesMovieContext( 14 serviceProvider.GetRequiredService< 15 DbContextOptions<RazorPagesMovieContext>>())) 16 { 17 // Look for any movies. 18 if (context.Movie.Any()) 19 { 20 return; // DB has been seeded 21 } 22 23 context.Movie.AddRange( 24 new Movie 25 { 26 Title = "When Harry Met Sally", 27 ReleaseDate = DateTime.Parse("1989-2-12"), 28 Genre = "Romantic Comedy", 29 Price = 7.99M 30 }, 31 32 new Movie 33 { 34 Title = "Ghostbusters ", 35 ReleaseDate = DateTime.Parse("1984-3-13"), 36 Genre = "Comedy", 37 Price = 8.99M 38 }, 39 40 new Movie 41 { 42 Title = "Ghostbusters 2", 43 ReleaseDate = DateTime.Parse("1986-2-23"), 44 Genre = "Comedy", 45 Price = 9.99M 46 }, 47 48 new Movie 49 { 50 Title = "Rio Bravo", 51 ReleaseDate = DateTime.Parse("1959-4-15"), 52 Genre = "Western", 53 Price = 3.99M 54 } 55 ); 56 context.SaveChanges(); 57 } 58 } 59 } 60 }
第18-21行：如果DB中有任何电影，则会返回种子初始值设定项，并且不会添加任何电影。
添加种子初始值设定项：
打开Program.cs文件，修改Main方法：
1 using Microsoft.AspNetCore.Hosting; 2 using Microsoft.Extensions.DependencyInjection; 3 using Microsoft.Extensions.Hosting; 4 using Microsoft.Extensions.Logging; 5 using RazorPagesMovie.Models; 6 using System; 7 8 namespace RazorPagesMovie 9 { 10 public class Program 11 { 12 public static void Main(string[] args) 13 { 14 var host = CreateHostBuilder(args).Build(); 15 16 using (var scope = host.Services.CreateScope()) 17 { 18 var services = scope.ServiceProvider; 19 20 try 21 { 22 SeedData.Initialize(services); 23 } 24 catch (Exception ex) 25 { 26 var logger = services.GetRequiredService<ILogger<Program>>(); 27 logger.LogError(ex, "An error occurred seeding the DB."); 28 } 29 } 30 31 host.Run(); 32 33 } 34 35 public static IHostBuilder CreateHostBuilder(string[] args) => 36 Host.CreateDefaultBuilder(args) 37 .ConfigureWebHostDefaults(webBuilder => 38 { 39 webBuilder.UseStartup<Startup>(); 40 }); 41 } 42 }
4、测试
1、删除数据库中我们刚才录入的数据：既可以从数据库中直接删除，也可以通过delete页面进行
2、退出IIS Express
3、再次按下ctrl+F5，运行。我们发现，即使我们已经完全删除录入的记录，页面上还是还是有记录，这就是数据库的种子：
下一节，我们介绍数据的展示