c#: 没有注册 *Context 类型的服务。 数据库连接问题

Question

我是 C# 新手，尝试使用 ASP.NET 核心将数据库连接添加到 MVC 项目：

模型：

• 实体类用户：

   public class User { public string Name { get; set;} public string LastName { get; set; } }

• 语境：

   using Microsoft.EntityFrameworkCore; namespace Forum.Models { public sealed class ForumContext : DbContext { public DbSet<User> Users { get; set;} public ForumContext(DbContextOptions<ForumContext> options) : base(options) { Database.EnsureCreated(); } protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) { optionsBuilder.UseMySql("server=localhost;UserId=root;Password=password;database=forum1;"); } } }

• 类 - 初始化程序：

   public static class SampleData { public static void Initialize(ForumContext context) { if (!context.Users.Any()) { context.Users.AddRange( new User() { LastName = "last name", Name = "Name" } ); } } }

配置和执行：

• appsettings.json：

   { "ConnectionStrings": { "DefaultConnection": "server=localhost;port=3306;user=root;password=password;database=forum1" }, "Logging": { "LogLevel": { "Default": "Information", "Microsoft": "Warning", "Microsoft.Hosting.Lifetime": "Information" } }, "AllowedHosts": "*" }

• 在Sturtup.cs类中，我只修改了 MySqlConnection 注入的ConfigureService方法：

   public void ConfigureServices(IServiceCollection services) { services.AddControllersWithViews(); services.AddTransient<MySqlConnection>(_ => new MySqlConnection(Configuration["ConnectionStrings:Default"])); }

• 和类Program.cs：

   public class Program { public static void Main(string[] args) { var host = CreateHostBuilder(args).Build(); using (var scope = host.Services.CreateScope()) { IServiceProvider provider = scope.ServiceProvider; try { //-------------------ERROR---------------------------- var context = provider.GetRequiredService<ForumContext>();//there is the exception was throwed SampleData.Initialize(context); } catch (Exception ex) { var logger = provider.GetRequiredService<ILogger<Program>>(); logger.LogError(ex, "An error occurred seeding the DB."); } } host.Run(); } public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); }); }

• 安装的软件包：

结果我有以下错误：

---

Answer 1

您必须在Startup.cs ConfigureServices中执行以下ConfigureServices

services.AddDbContext<{yourDBContext_Name}>(options =>
{
      options.UseMySql({Your Connection String});
      // If it is for Sql Server use options.UseSqlServer({Your Connection String});
});