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
原文地址：https://www.cnblogs.com/hiwuchong/p/12082339.html
时间： 2024-12-10 00:58:01