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처음 마이그레이션을 수행 할 때 Microsoft.Extensions.Hosting 서비스에 액세스하는 동안 오류가 발생했습니다.

debugcn 에 게시 Dev
7
멀미

나는 무엇이 잘못되었는지 이해하지 못한다. 나는 필드가 거의없는 매우 간단한 모델로 .net core mvc에서 간단한 간단한 crud를 만들려고합니다.

이것은 내 모델입니다

    public class Employee
    {
        [Key] public int EmployeeId { get; set; }

        [Required] public string FistName { get; set; }

        [Required] public string LastName { get; set; }

        public int PositionId { get; set; }
        public virtual Position Position { get; set; }

    }
public class Position
    {
        [Key]
        public int PositionId { get; set; }
        public string PositionName { get; set; }
        public ICollection<Employee> Employees { get; set; }
    }

그런 다음 앱 컨텍스트를 만듭니다.

public class EmployeeContext : DbContext
{
    public EmployeeContext(DbContextOptions<EmployeeContext> options)
        : base(options)
    {
    }

    public DbSet<Employee> Employees { get; set; }
    public DbSet<Position> Positions { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Employee>()
            .HasOne(e => e.Position)
            .WithMany()
            .HasForeignKey(e => e.PositionId);
    }
}

Startup.cs에 컨텍스트 등록 및 등록

 public void ConfigureServices(IServiceCollection services)
    {
        services.Configure<CookiePolicyOptions>(options =>
        {
            // This lambda determines whether user consent for non-essential cookies is needed for a given request.
            options.CheckConsentNeeded = context => true;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

        services.AddDbContext<EmployeeContext>(item =>item.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);                
        }

.csproj 및 program.cs의 파일 코드가 하나 더 필요할 수 있습니다.

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net461</TargetFramework>
    <DebugType>full</DebugType>
  </PropertyGroup>


  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore" Version="2.2.0" />
    <PackageReference Include="Microsoft.AspNetCore.CookiePolicy" Version="2.2.8" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.2.0" />
    <PackageReference Include="Microsoft.AspNetCore.StaticFiles" Version="2.2.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="3.1.2">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer.Design" Version="1.1.6" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.1.2">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.Extensions.Logging.Configuration" Version="3.1.2" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.1.1" />
  </ItemGroup>

</Project>

public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

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

그런 다음 먼저 마이그레이션을 시도하지만 매우 이상한 오류가 표시됩니다. Add-Migration FirstInit -verbose

Using project 'Crud'.
Using startup project 'Crud'.
Build started...
Build succeeded.
C:\.nuget\packages\microsoft.entityframeworkcore.tools\3.1.2\tools\net461\win-x86\ef.exe migrations add FirstInit --json --verbose --no-color --prefix-output --assembly C:\source\repos\Crud\Crud\bin\Debug\net461\Crud.exe --startup-assembly C:\source\repos\Crud\Crud\bin\Debug\net461\Crud.exe --project-dir C:\source\repos\Crud\Crud\ --language C# --working-dir C:\source\repos\Crud --root-namespace Crud
Using assembly 'Crud'.
Using startup assembly 'Crud'.
Using application base 'C:\source\repos\Crud\Crud\bin\Debug\net461'.
Using working directory 'C:\source\repos\Crud\Crud'.
Using root namespace 'Crud'.
Using project directory 'C:\source\repos\Crud\Crud\'.
Using configuration file 'C:\source\repos\Crud\Crud\bin\Debug\net461\Crud.exe.config'.
Using assembly 'Crud'.
Using startup assembly 'Crud'.
Using application base 'C:\source\repos\Crud\Crud\bin\Debug\net461'.
Using working directory 'C:\source\repos\Crud\Crud'.
Using root namespace 'Crud'.
Using project directory 'C:\source\repos\Crud\Crud\'.
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider...
Finding Microsoft.Extensions.Hosting service provider...
Using environment 'Development'.
System.TypeLoadException: There is no implementation of the GetItem method in the type "Microsoft.AspNetCore.Mvc.Razor.Internal.FileProviderRazorProjectFileSystem" from assembly "Microsoft.AspNetCore.Mvc.Razor, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60".
   в Microsoft.Extensions.DependencyInjection.MvcRazorMvcCoreBuilderExtensions.AddRazorViewEngineServices(IServiceCollection services)
   в Microsoft.Extensions.DependencyInjection.MvcRazorMvcCoreBuilderExtensions.AddRazorViewEngine(IMvcCoreBuilder builder)
   в Microsoft.Extensions.DependencyInjection.MvcServiceCollectionExtensions.AddMvc(IServiceCollection services)
   в Crud.Startup.ConfigureServices(IServiceCollection services) в C:\source\repos\Crud\Crud\Startup.cs:строка 38
--- End the stack trace from the previous location where the exception occurred ---
   в System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   в Microsoft.AspNetCore.Hosting.ConventionBasedStartup.ConfigureServices(IServiceCollection services)
   в Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices()
   в Microsoft.AspNetCore.Hosting.Internal.WebHost.Initialize()
   в Microsoft.AspNetCore.Hosting.WebHostBuilder.Build()
An error occurred while accessing the Microsoft.Extensions.Hosting services. Continuing without the application service provider. Error: There is no implementation of the GetItem method in the type "Microsoft.AspNetCore.Mvc.Razor.Internal.FileProviderRazorProjectFileSystem" from assembly "Microsoft.AspNetCore.Mvc.Razor, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60".
No application service provider was found.
Finding DbContext classes in the project...
Found DbContext 'EmployeeContext'.
Microsoft.EntityFrameworkCore.Design.OperationException: Unable to create an object of type 'EmployeeContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728 ---> System.MissingMethodException:There are no parameterless constructors defined for this object..
   в System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   в System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   в System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   в System.Activator.CreateInstance(Type type, Boolean nonPublic)
   в System.Activator.CreateInstance(Type type)
   в Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_3.<FindContextTypes>b__13()
   --- End trace of internal exception stack ---
   в Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_3.<FindContextTypes>b__13()
   в Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
   в Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
   в Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)
   в Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
   в Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   в Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   в Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Unable to create an object of type 'EmployeeContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

이 세 줄에 무슨 문제가 있습니까?

셰 르빈이 바리

EF는 Main을 실행하지 않고 CreateWebHostBuilder 또는 BuildWebHost를 호출합니다. 따라서 Iconfiguration은 null입니다.

IDesignTimeDbContextFactory 에서 상속 된 새 클래스를 만듭니다 .

public class EmployeeContext : DbContext
{
//Dbcontext implementation
}

public class EmployeeFactory : IDesignTimeDbContextFactory<EmployeeContext>
{
    public EmployeeContext CreateDbContext(string[] args)
    {
        var optionsBuilder = new DbContextOptionsBuilder<EmployeeContext>();
        optionsBuilder.UseSqlServer("your connection string");

        return new EmployeeContext(optionsBuilder.Options);
    }
}

IHostBuilder를 사용하는 새로운 .net 코어 EF를 사용하고 있습니다 (귀하의 것과 같은 이전 버전에서 공급자는 IWebHostBuilder입니다). 도구는 먼저 Program.CreateHostBuilder ()를 호출하고 Build ()를 호출 한 다음 Services 속성에 액세스하여 서비스 공급자를 얻으려고합니다.

EF는 모델을 빌드하고 애플리케이션을 시작하지 않고 DbContext를 사용해야합니다. EF가 메서드를 호출 할 때 구성 서비스가 여전히 null이므로 오류가 발생합니다.

패키지를 설치했는지 확인하십시오

Microsoft.EntityFrameworkCore.Tools

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