c# - c#：没有注册类型 *Context 的服务。数据库连接问题

Question

我是 C# 新手，并尝试使用 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 - 初始化器：

   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ConfigureService了 MySqlConnection 注入的方法：

    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>();
            });
  }
  

• 已安装的软件包：

结果我有以下错误：

---

标签： c#mysqlentity-framework-core

Answer 1

您必须执行以下ConfigureServices操作Startup.cs

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