为什么我在 ASP.NET Core 6 C# 中收到此错误？

Question

When I want to create a controller I get this error:

enter image description here

There was an error running the selected code generator:
'Unable to resolve service for type 'Microsoft.EntityFrameworkCore.Db.ContextOptions'1[DATAMain.DB] while attempting to activate 'DataMain.DB'

DB.cs

    using Microsoft.AspNetCore.Identity;
    using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
    using Microsoft.EntityFrameworkCore;
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    
    namespace DataMain
    {
        public class DB : IdentityDbContext<IdentityUser, IdentityRole, string>
        {
            public DB(DbContextOptions<DB> options) : base(options)
            {
            }

            public DbSet<Category> Categories { get; set; }
        }
     }

Answer 1

Be sure to have the Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore package installed.

then register the service :

using ContosoUniversity.Data;
using Microsoft.EntityFrameworkCore;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace ContosoUniversity
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
    -->     services.AddDbContext<SchoolContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

   -->      services.AddDatabaseDeveloperPageExceptionFilter();

            services.AddControllersWithViews();
        }

read documentation on microsoft : https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/intro?view=aspnetcore-6.0