[英]Cannot resolve scoped service from root provider - solution to error?
我正在使用 .Net MVC 编写一个应用程序,以将数据库中的数据打印到页面上。 我已经安装了 EntityFrameworkCore SqlServer 包和 EntityFrameworkCore Tools 包,创建了一些数据库类,创建了一个存储库类并创建并应用了数据库迁移。
但是,当我尝试运行该行时:
ApplicationDbContext context = app.ApplicationServices.GetRequiredService<ApplicationDbContext>()
我收到一个错误:“System.InvalidOperationException: 'Cannot resolve scoped service 'SportsStore.Models.ApplicationDbContext' from root provider.'”
我知道这与解决程序范围有关,但我不确定要进行哪些代码更改。
这是完整的文件 SeedData.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
namespace SportsStore.Models
{
public static class SeedData
{
public static void EnsurePopulated(IApplicationBuilder app)
{
ApplicationDbContext context = app.ApplicationServices.GetRequiredService<ApplicationDbContext>();
if (!context.Products.Any())
{
context.Products.AddRange(
new Product
{
Name = "Kayak",
Description = "A boat for one person",
Category = "Watersports",
Price = 275
},
new Product
{
Name = "Lifejacket",
Description = "Protective and fashionable",
Category = "Watersports", Price = 48.95m
},
new Product
{
Name = "Soccer Ball",
Description = "FIFA-approved size and weight",
Category = "Soccer", Price = 19.50m
},
new Product
{
Name = "Corner Flags",
Description = "Give your playing field a professional touch",
Category = "Soccer",
Price = 34.95m
},
new Product
{
Name = "Stadium",
Description = "Flat-packed 35,000-seat stadium",
Category = "Soccer",
Price = 79500
},
new Product
{
Name = "Thinking Cap",
Description = "Improve brain efficiency by 75%",
Category = "Chess",
Price = 16
},
new Product
{
Name = "Unsteady Chair",
Description = "Secretly give your opponent a disadvantage",
Category = "Chess",
Price = 75
},
new Product
{
Name = "Bling-Bling King",
Description = "Gold-plated, diamond-studded King",
Category = "Chess",
Price = 1200
}
);
context.SaveChanges();
}
}
}
}
这是我的数据库上下文类 ApplicationDbContext.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
namespace SportsStore.Models
{
public class ApplicationDbContext : DbContext
{
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
: base(options) {} // provides access to Entity Framework Core's underlying functionality
public DbSet<Product> Products { get; set; } // Provides access to the Product objects in the database.
}
}
// 存储库类 - EFProductRepository.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace SportsStore.Models{
public class EFProductRepository : IProductRepository
{
private ApplicationDbContext context;
public EFProductRepository(ApplicationDbContext ctx)
{
context = ctx;
}
public IEnumerable<Product> Products => context.Products; // maps the products property defined by IProductRepository onto Products property defined by the ApplicationDbContext class.
}
}
// 启动.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using SportsStore.Models;
using Microsoft.Extensions.Configuration;
using Microsoft.EntityFrameworkCore;
namespace SportsStore
{
public class Startup
{
IConfigurationRoot Configuration;
public Startup(IHostEnvironment env)
{
Configuration = new ConfigurationBuilder()
.SetBasePath(env.ContentRootPath)
.AddJsonFile("appsettings.json").Build();
}
// This method gets called by the runtime. Use this method to add services to the container.
// For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(
Configuration["Data:SportStoreProducts:ConnectionString"])); // loads configuration settings in the appsettings.json file and makes them available through a property called Configuration.
services.AddTransient<IProductRepository,
EFProductRepository>();
services.AddMvc(options => options.EnableEndpointRouting = false);
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseStatusCodePages();
app.UseStaticFiles();
}
app.UseRouting();
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Product}/{action=List}/{id?}");
});
SeedData.EnsurePopulated(app);
}
}
}
如果有任何有用的建议,请告诉我! 谢谢,
问候,
罗伯特
英国伦敦
您需要在Program类中禁用范围验证:
public class Program {
...
public static IWebHost BuildWebHost(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.UseDefaultServiceProvider(options =>
options.ValidateScopes = false)
.Build();
}
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