2.NET Core设定数据库种子

 

1.使用以下代码在 Models 文件夹中创建一个名为 SeedData 的新类：

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Linq;

namespace RazorPagesMovie.Models
{
public static class SeedData
{
public static void Initialize(IServiceProvider serviceProvider)
{
using (var context = new RazorPagesMovieContext(
serviceProvider.GetRequiredService<
DbContextOptions<RazorPagesMovieContext>>()))
{
// 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("1989-2-12"),
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();
}
}
}
}

2.添加种子初始值设定项

在 Program.cs 中，修改 Main 方法以执行以下操作：
从依赖关系注入容器获取数据库上下文实例。
调用 seed 方法，并将上下文传递给它。
Seed 方法完成时释放上下文。
下面的代码显示更新后的 Program.cs 文件。

using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using RazorPagesMovie.Models;
using System;
using Microsoft.EntityFrameworkCore;

namespace RazorPagesMovie
{
public class Program
{
public static void Main(string[] args)
{
var host = CreateWebHostBuilder(args).Build();

using (var scope = host.Services.CreateScope())
{
var services = scope.ServiceProvider;

try
{
var context=services.
GetRequiredService<RazorPagesMovieContext>();
context.Database.Migrate();
SeedData.Initialize(services);
}
catch (Exception ex)
{
var logger = services.GetRequiredService<ILogger<Program>>();
logger.LogError(ex, "An error occurred seeding the DB.");
}
}

host.Run();
}

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>();
}
}