从.net Core WebApi中的startup.cs访问HttpContextAccessor

我正在将异常记录到 asp.net core 中的数据库中。 MyDbContext 采用 HttpContextAccessor 参数。因此，我将 HttpContextAccessor 发送到 MyDbContext.cs 以访问我的 JWT。但是，我无法从 Startup.cs 访问我的 HttpContextAccessor。我怎样才能实现这个目标？

启动.cs

   public void ConfigureServices(IServiceCollection services)
    {
        services.AddHttpContextAccessor();
        services.AddMvc();
        services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
        services.AddDbContext<MyDbContext>();
        services.AddTransient<IUnitOfWork, UnitOfWork>();
    }


    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
         app.UseExceptionHandler(builder => builder.Run(async context =>
         {
             var error = context.Features.Get<IExceptionHandlerFeature>();

             context.Response.AddApplicationError(error,???????);//I want access HttpContextAccessor
             await context.Response.WriteAsync(error.Error.Message);
         }));

        app.UseHttpsRedirection();
        app.UseMvc();
    }

异常助手.cs

 public static class ExceptionHelper
    {
        public static async Task AddApplicationError(this HttpResponse response, IExceptionHandlerFeature error, IHttpContextAccessor httpContextAccessor)
        {
           Log log = new Log();
           log.Message = error.Error.Message;          

           MyDbContext context = new MyDbContext(null, httpContextAccessor);
           UnitOfWork uow = new UnitOfWork(context);
           uow.LogRepo.AddOrUpdate(log);
           await uow.CompleteAsync(false);               
        }
    }

我的DbContext

public class MyDbContext : DbContext
{
    private readonly IHttpContextAccessor _httpContextAccessor;

    public MyDbContext(DbContextOptions<MyDbContext> options, IHttpContextAccessor httpContextAccessor)
        : base(GetOptions())
    {
        _httpContextAccessor = httpContextAccessor;
    }

    private static DbContextOptions GetOptions()
    {
        return SqlServerDbContextOptionsExtensions.UseSqlServer(new DbContextOptionsBuilder(), "server=asd; database=; user id=asd; password=1234").Options;
    }

    public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        var token = _httpContextAccessor.HttpContext.Request.Headers["Authorization"];
        var audits = AuditHelper.AddAuditLog(base.ChangeTracker, token);
        return (await base.SaveChangesAsync(true, cancellationToken));
    }
}

你可以将你需要的任何东西注入到Configure方法。您已经使用以下行将其添加到服务集合中：

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

因此，您需要做的就是将其添加到方法的参数列表中，如下所示：

public void Configure(IApplicationBuilder app, IHostingEnvironment env, IHttpContextAccessor accessor)
{
    // make use of it here
}

顺便说一句：我还想指出，您手动创建一个实例有点代码味道DbContext当您使用依赖注入时，在静态帮助器类中。

更新以回复评论

为了稍微整理一下，我将首先更改您的启动来配置 DbContext，如下所示：

public class Startup
{
    private readonly IConfiguration configuration;

    public Startup(IConfiguration configuration)
    {
        this.configuration = configuration;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        // register other things here...

        services.AddDbContext<DataContext>(o => o.UseSqlServer(
            config.GetConnectionString("MyConnectionString") // from appsettings.json
        ));
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        // set up app here...
    }
}

然后您可以删除.GetOptions()方法来自MyDbContext，并将构造函数更改为：

public MyDbContext(DbContextOptions<MyDbContext> options, IHttpContextAccessor httpContextAccessor)
    : base(options)
{
    _httpContextAccessor = httpContextAccessor;
}

然后你注入一个实例MyDbContext进入任何需要访问它的类。问题是（据我所知）DI 不能很好地处理静态类/方法，并且您正在使用扩展方法HttpResponse记录您的错误。

在我看来，最好创建一个类来负责记录错误并依赖于您的MyDbContext并将其注入Configure method:

public class ErrorLogger
{
    private MyDataContext db;

    public ErrorLogger(MyDataContext db) => this.db = db;

    public void LogError(IExceptionHandlerFeature error)
    {
        Log log = new Log();
        log.Message = error.Error.Message; 

        UnitOfWork uow = new UnitOfWork(this.db);
        uow.LogRepo.AddOrUpdate(log);
        await uow.CompleteAsync(false);
    }
}

像注册其他东西一样将其注册到 DI 容器中，然后将其注入Configure而不是 HTTP 访问器：

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ErrorLogger logger)
{
     app.UseExceptionHandler(builder => builder.Run(async context =>
     {
         var error = context.Features.Get<IExceptionHandlerFeature>();
         logger.LogError(error);
         await context.Response.WriteAsync(error.Error.Message);
     }));
}

这个我没测试过，也不熟悉.UseExceptionHandler(...)因为我使用应用程序洞察来记录异常等（如果您还没有看到它，请看一下）。需要注意的一件事是您的依赖项的范围；你的 DbContext 将是Scoped默认情况下（我认为你应该保持这种方式），这意味着你不能将它注入Singleton对象。