c# - 在 .net Core WebApi 中从 startup.cs 访问 HttpContextAccessor

Question

我正在将异常记录到 asp.net core 中的数据库。 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。我怎样才能做到这一点？

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();
    }

ExceptionHelper.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);               
        }
    }

MyDbContext

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));
    }
}

Answer 1

您可以将所需的任何内容注入(inject)Configure 方法。您已经使用此行将其添加到服务集合中:

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

所以您需要做的就是将它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:我还要指出，当您使用依赖项注入(inject)时，您在静态帮助程序类中手动创建 DbContext 的实例有点代码味道。

响应评论更新

为了稍微整理一下，我将首先更改您的启动以配置 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...
    }
}

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

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

然后将 MyDbContext 的实例注入(inject)到任何需要访问它的类中。问题是(据我所知)DI 不能很好地与静态类/方法一起使用，并且您正在 HttpResponse 上使用扩展方法来记录您的错误。

在我看来，最好创建一个类来记录依赖于 MyDbContext 的错误，并将其注入(inject)到 Configure 方法中:

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使用 DI 容器注册它，然后将它注入(inject) 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);
     }));
}

我没有对此进行测试，并且我不熟悉 .UseExceptionHandler(...)，因为我使用 application insights 来记录异常等(如果您还没有看到，请查看它它)。需要注意的一件事是依赖项的范围；默认情况下，您的 DbContext 将被 Scoped(我认为您应该保持这种状态)，这意味着您不能将其注入(inject) Singleton 对象。