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问题描述

当我尝试在 Startup.cs 文件的 Configure 方法中使用自定义DbContext时,收到以下异常。我在2.0.0-preview1-005977版本中使用ASP.NET Core

I receive following exception when I try to use custom DbContext in Configure method in Startup.cs file. I use ASP.NET Core in version 2.0.0-preview1-005977

此异常

这是我的 ConfigureServices Configure 方法。

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<CommunicatorContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
    services.AddCookieAuthentication();
    services.Configure<LdapConfig>(Configuration.GetSection("Ldap"));
    services.AddScoped<ILdapService, LdapService>();
    services.AddMvc();
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, CommunicatorContext dbContext, ILdapService ldapService)
{
    app.UseAuthentication();
    app.UseWebSockets();
    app.Use(async (context, next) =>
    {
        if (context.Request.Path == "/ws")
        {
            if (context.WebSockets.IsWebSocketRequest)
            {
                WebSocket webSocket = await context.WebSockets.AcceptWebSocketAsync();
                await Echo(context, webSocket);
            }
            else
            {
                context.Response.StatusCode = 400;
            }
        }
        else
        {
            await next();
        }
    });
    app.UseMvc();
    DbInitializer.Initialize(dbContext, ldapService);
}


推荐答案

报价文档

ASP.NET Core依赖项注入在$期间提供应用程序服务b $ b应用程序的启动。您可以通过在$$$$$构造函数或其中的配置之一中将
作为适当的接口作为参数添加到$$$$ Start $
类中,以请求这些服务。 或 ConfigureServices 方法。

ASP.NET Core dependency injection provides application services during an application's startup. You can request these services by including the appropriate interface as a parameter on your Startup class's constructor or one of its Configure or ConfigureServices methods.

查看 Startup 类,按照它们调用
的顺序,可能需要以下服务作为
参数:

Looking at each method in the Startup class in the order in which they are called, the following services may be requested as parameters:


  • 在构造函数中: IHostingEnvironment ILoggerFactory

  • ConfigureServices 方法中: IServiceCollection

  • 在<$ c中$ c>配置方法: IApplicationBuilder IHostingEnvironment
    ILoggerFactory IApplicationLifetime

  • In the constructor: IHostingEnvironment, ILoggerFactory
  • In the ConfigureServices method: IServiceCollection
  • In the Configure method: IApplicationBuilder, IHostingEnvironment, ILoggerFactory, IApplicationLifetime

您正在尝试解决启动期间不可用的服务,

You are trying to resolve services that are not available during startup,

...CommunicatorContext dbContext, ILdapService ldapService) {

这将为您提供错误信息。如果需要访问实现,则需要执行以下操作之一:

which will give you the errors you are getting. If you need access to the implementations then you need to do one of the following:


  1. 修改 ConfigureServices 方法,然后从服务集合中访问它们。即

  1. Modify the ConfigureServices method and access them there from the service collection. i.e.

public IServiceProvider ConfigureServices(IServiceCollection services) {
    services.AddDbContext<CommunicatorContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
    services.AddCookieAuthentication();
    services.Configure<LdapConfig>(Configuration.GetSection("Ldap"));
    services.AddScoped<ILdapService, LdapService>();
    services.AddMvc();

    // Build the intermediate service provider
    var serviceProvider = services.BuildServiceProvider();

    //resolve implementations
    var dbContext = serviceProvider.GetService<CommunicatorContext>();
    var ldapService = serviceProvider.GetService<ILdapService>();
    DbInitializer.Initialize(dbContext, ldapService);

    //return the provider
    return serviceProvider();
}


  • 修改 ConfigureServices 方法返回IServiceProvider,配置方法获取 IServiceProvider ,然后在那里解析您的依赖项。即

  • Modify the ConfigureServices method to return IServiceProvider, Configure method to take a IServiceProvider and then resolve your dependencies there. i.e.

    public IServiceProvider ConfigureServices(IServiceCollection services) {
        services.AddDbContext<CommunicatorContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
        services.AddCookieAuthentication();
        services.Configure<LdapConfig>(Configuration.GetSection("Ldap"));
        services.AddScoped<ILdapService, LdapService>();
        services.AddMvc();
    
        // Build the intermediate service provider then return it
        return services.BuildServiceProvider();
    }
    
    public void Configure(IApplicationBuilder app, IHostingEnvironment env,
                          ILoggerFactory loggerFactory, IServiceProvider serviceProvider) {
    
        //...Other code removed for brevity
    
        app.UseMvc();
    
        //resolve dependencies
        var dbContext = serviceProvider.GetService<CommunicatorContext>();
        var ldapService = serviceProvider.GetService<ILdapService>();
        DbInitializer.Initialize(dbContext, ldapService);
    }
    


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    08-24 00:35