c# - 没有注册类型 'Microsoft.AspNetCore.Hosting.IHostingEnvironment' 的服务

Question

当我想为 ASP MVC Core 2 项目触发 add-migration 命令时遇到问题。

No service for type 'Microsoft.AspNetCore.Hosting.IHostingEnvironment' has been registered.

这是我的Startup.cs:

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

    public IConfiguration Configuration { get; set; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContextPool<SampleArchContext>((serviceProvider, optionsBuilder) =>
        {
            optionsBuilder.UseInternalServiceProvider(serviceProvider); // It's added to access services from the dbcontext, remove it if you are using the normal `AddDbContext` and normal constructor dependency injection.
        });

        services.AddMvc(options =>
        {
            options.AllowEmptyInputInBodyModelBinding = true;
        }).AddJsonOptions(jsonOptions =>
        {
            jsonOptions.SerializerSettings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;
        });
    }

    public void Configure(
        ILoggerFactory loggerFactory,
        IApplicationBuilder app,
        IHostingEnvironment env)
    {

        if (env.IsDevelopment())
        {
            var builder = new ConfigurationBuilder()
             .SetBasePath(env.ContentRootPath)
             .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
             .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
             .AddEnvironmentVariables();
            Configuration = builder.Build();

            app.UseDeveloperExceptionPage();
            app.UseBrowserLink();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
        }

        app.UseStaticFiles();

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });
        app.UseFileServer(new FileServerOptions
        {
            FileProvider = new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), "bower_components")),
            RequestPath = "/bower_components",
            EnableDirectoryBrowsing = false
        });            
    }
}

程序.cs:

public class Program
{
    public static void Main(string[] args)
    {
        var host = new WebHostBuilder()
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .ConfigureAppConfiguration((hostingContext, config) =>
            {
                var env = hostingContext.HostingEnvironment;
                config.SetBasePath(env.ContentRootPath);
                config.AddInMemoryCollection(new[]
                       {
                         new KeyValuePair<string,string>("the-key", "the-value")
                       })
                       .AddJsonFile("appsettings.json", reloadOnChange: true, optional: false)
                       .AddJsonFile($"appsettings.{env}.json", optional: true)
                       .AddEnvironmentVariables();
            })
            .ConfigureLogging((hostingContext, logging) =>
            {
                logging.AddDebug();
                logging.AddConsole();
            })
            .UseIISIntegration()
            .UseDefaultServiceProvider((context, options) =>
            {
                options.ValidateScopes = context.HostingEnvironment.IsDevelopment();
            })
            .UseStartup<Startup>()
            .Build();

        host.Run();
    }
}

上下文:

public interface IContext
{
    DbSet<Person> Persons { get; set; }
    DbSet<Country> Countries { get; set; }
    DbSet<TEntity> Set<TEntity>() where TEntity : class;
    EntityEntry<TEntity> Entry<TEntity>(TEntity entity) where TEntity : class;
    int SaveChanges();
}
public class SampleArchContext : DbContext, IContext
{
    public SampleArchContext(DbContextOptions<SampleArchContext> options)
        : base(options)
    { }
    public DbSet<Person> Persons { get; set; }
    public DbSet<Country> Countries { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.Entity<Country>(build =>
        {
            build.Property(category => category.Name).HasMaxLength(450).IsRequired();
        });
    }
    public override int SaveChanges()
    {
        var modifiedEntries = ChangeTracker.Entries()
            .Where(x => x.Entity is IAuditableEntity
                && (x.State == EntityState.Added || x.State == EntityState.Modified));

        foreach (var entry in modifiedEntries)
        {
            IAuditableEntity entity = entry.Entity as IAuditableEntity;
            if (entity != null)
            {
                string identityName = Thread.CurrentPrincipal.Identity.Name;
                DateTime now = DateTime.UtcNow;

                if (entry.State == EntityState.Added)
                {
                    entity.CreatedBy = identityName;
                    entity.CreatedDate = now;
                }
                else
                {
                    base.Entry(entity).Property(x => x.CreatedBy).IsModified = false;
                    base.Entry(entity).Property(x => x.CreatedDate).IsModified = false;
                }
                entity.UpdatedBy = identityName;
                entity.UpdatedDate = now;
            }
        }

        return base.SaveChanges();
    }
}
public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<SampleArchContext>
{    
    public SampleArchContext CreateDbContext(string[] args)
    {
        var service = new ServiceCollection();
        service.AddOptions();
        //service.AddScoped<IHostingEnvironment, CustomHostingEnvironment>();
        service.AddSingleton<ILoggerFactory, LoggerFactory>();
        var serviceProvider = service.BuildServiceProvider();
        var hostingEnvirement = serviceProvider.GetRequiredService<IHostingEnvironment>();
        IConfigurationRoot configuration = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
           .SetBasePath(basePath: hostingEnvirement.ContentRootPath)
           //.SetBasePath(Directory.GetCurrentDirectory())
            .Build();
        service.AddSingleton(provider => configuration);
        serviceProvider = service.BuildServiceProvider();

        var builder = new DbContextOptionsBuilder<SampleArchContext>();
        var connectionString = configuration.GetConnectionString("AppDbContextConnection");
        builder.UseSqlServer(connectionString);
        return new SampleArchContext(builder.Options);
    }
}

这是我的 appsetting.json :

appsetting.json :

{
  "ConnectionStrings": {
    "AppDbContextConnection": "Server=localhost; Database=CoreDbName;Trusted_Connection=True; MultipleActiveResultSets=true"
  },
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Warning"
    }
  }
}

我搜索了很多，但找不到解决这个问题的方法，我该如何解决？

Answer 1

ASP.NET Core 2 中有一个新的应用程序模式。请参阅 Migrating from ASP.NET Core 1.x to ASP.NET Core 2.0了解详情。

EF Core 不再尝试直接调用 Startup.ConfigureServices()。在 2.0 版中，它将查找静态 Program.BuildWebHost() 方法并从中获取您的应用程序服务。

要采用新模式，请将您的 Program 类更新为如下所示。

public class Program
{
    public static IWebHost BuildWebHost(string[] args)
    {
        var host = new WebHostBuilder()
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .ConfigureAppConfiguration((hostingContext, config) =>
            {
                var env = hostingContext.HostingEnvironment;
                config.SetBasePath(env.ContentRootPath);
                config.AddInMemoryCollection(new[]
                       {
                         new KeyValuePair<string,string>("the-key", "the-value")
                       })
                       .AddJsonFile("appsettings.json", reloadOnChange: true, optional: false)
                       .AddJsonFile($"appsettings.{env}.json", optional: true)
                       .AddEnvironmentVariables();
            })
            .ConfigureLogging((hostingContext, logging) =>
            {
                logging.AddDebug();
                logging.AddConsole();
            })
            .UseIISIntegration()
            .UseDefaultServiceProvider((context, options) =>
            {
                options.ValidateScopes = context.HostingEnvironment.IsDevelopment();
            })
            .UseStartup<Startup>()
            .Build();

        return host;
    }

    public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }
}