在ASP.NET Core中访问当前的HttpContext

我需要使用HttpContext静态方法或实用程序服务来访问当前数据。

使用经典的ASP.NET MVC和System.Web，我将只用于HttpContext.Current静态访问上下文。但是如何在ASP.NET Core中做到这一点？

HttpContext.Current在ASP.NET Core中已经不存在了，但是IHttpContextAccessor您可以注入新 的依赖项并用于检索当前的依赖项HttpContext：

public class MyComponent : IMyComponent
{
    private readonly IHttpContextAccessor _contextAccessor;

    public MyComponent(IHttpContextAccessor contextAccessor)
    {
        _contextAccessor = contextAccessor;
    }

    public string GetDataFromSession()
    {
        return _contextAccessor.HttpContext.Session.GetString(*KEY*);
    }
}

死灵法师。
是的，您可以
为那些大规模迁移的人提供秘诀垃圾代码块（叹气，弗洛伊德式的滑动）。
以下方法是骇客的邪恶手段，它正积极地执行satan的快速工作（在.NET Core框架开发人员看来），但它可以起作用：

在 public class Startup

添加一个属性

public IConfigurationRoot Configuration { get; }

然后将单例IHttpContextAccessor添加到ConfigureServices中的DI。

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<Microsoft.AspNetCore.Http.IHttpContextAccessor, Microsoft.AspNetCore.Http.HttpContextAccessor>();

然后在配置中

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

添加DI参数IServiceProvider svp，因此该方法如下所示：

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

接下来，为System.Web创建替换类：

namespace System.Web
{

    namespace Hosting
    {
        public static class HostingEnvironment 
        {
            public static bool m_IsHosted;

            static HostingEnvironment()
            {
                m_IsHosted = false;
            }

            public static bool IsHosted
            {
                get
                {
                    return m_IsHosted;
                }
            }
        }
    }


    public static class HttpContext
    {
        public static IServiceProvider ServiceProvider;

        static HttpContext()
        { }


        public static Microsoft.AspNetCore.Http.HttpContext Current
        {
            get
            {
                // var factory2 = ServiceProvider.GetService<Microsoft.AspNetCore.Http.IHttpContextAccessor>();
                object factory = ServiceProvider.GetService(typeof(Microsoft.AspNetCore.Http.IHttpContextAccessor));

                // Microsoft.AspNetCore.Http.HttpContextAccessor fac =(Microsoft.AspNetCore.Http.HttpContextAccessor)factory;
                Microsoft.AspNetCore.Http.HttpContext context = ((Microsoft.AspNetCore.Http.HttpContextAccessor)factory).HttpContext;
                // context.Response.WriteAsync("Test");

                return context;
            }
        }


    } // End Class HttpContext 


}

现在在Configure中，在其中添加IServiceProvider svp，将服务提供者保存到刚创建的虚拟类System.Web.HttpContext（System.Web.HttpContext.ServiceProvider）中的静态变量“ ServiceProvider”中

并将HostingEnvironment.IsHosted设置为true

System.Web.Hosting.HostingEnvironment.m_IsHosted = true;

这本质上就是System.Web所做的，只是您从未见过（我猜该变量被声明为内部变量而不是公共变量）。

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IServiceProvider svp)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    ServiceProvider = svp;
    System.Web.HttpContext.ServiceProvider = svp;
    System.Web.Hosting.HostingEnvironment.m_IsHosted = true;


    app.UseCookieAuthentication(new CookieAuthenticationOptions()
    {
        AuthenticationScheme = "MyCookieMiddlewareInstance",
        LoginPath = new Microsoft.AspNetCore.Http.PathString("/Account/Unauthorized/"),
        AccessDeniedPath = new Microsoft.AspNetCore.Http.PathString("/Account/Forbidden/"),
        AutomaticAuthenticate = true,
        AutomaticChallenge = true,
        CookieSecure = Microsoft.AspNetCore.Http.CookieSecurePolicy.SameAsRequest

       , CookieHttpOnly=false

    });

像在ASP.NET Web窗体中一样，当您尝试访问没有HttpContext的HttpContext时（例如，它曾经Application_Start在global.asax中），您将获得NullReference 。

我再次强调，这只有在您实际添加

services.AddSingleton<Microsoft.AspNetCore.Http.IHttpContextAccessor, Microsoft.AspNetCore.Http.HttpContextAccessor>();

就像我写的那样。
欢迎使用DI模式中的ServiceLocator模式；）
有关风险和副作用，请咨询您的住院医生或药剂师-或在github.com/aspnet上研究.NET Core的来源，并进行一些测试。

也许更可维护的方法是添加此帮助程序类

namespace System.Web
{

    public static class HttpContext
    {
        private static Microsoft.AspNetCore.Http.IHttpContextAccessor m_httpContextAccessor;


        public static void Configure(Microsoft.AspNetCore.Http.IHttpContextAccessor httpContextAccessor)
        {
            m_httpContextAccessor = httpContextAccessor;
        }


        public static Microsoft.AspNetCore.Http.HttpContext Current
        {
            get
            {
                return m_httpContextAccessor.HttpContext;
            }
        }


    }


}

然后在Startup-> Configure中调用HttpContext.Configure

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IServiceProvider svp)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();


    System.Web.HttpContext.Configure(app.ApplicationServices.
        GetRequiredService<Microsoft.AspNetCore.Http.IHttpContextAccessor>()
    );

只是为了增加其他答案...

在ASP.NET 2.1的核心，还有的AddHttpContextAccessor扩展方法，将注册IHttpContextAccessor与正确的生命周期：

public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpContextAccessor();

    // Other code...
}

我想到的最合法的方法是在静态实现中注入IHttpContextAccessor，如下所示：

public static class HttpHelper
{
     private static IHttpContextAccessor _accessor;
     public static void Configure(IHttpContextAccessor httpContextAccessor)
     {
          _accessor = httpContextAccessor;
     }

     public static HttpContext HttpContext => _accessor.HttpContext;
}

然后在启动配置中分配IHttpContextAccessor应该可以完成这项工作。

HttpHelper.Configure(app.ApplicationServices.GetRequiredService<IHttpContextAccessor>());

我想您还应该注册服务单例：

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

根据本文的介绍：在ASP.NET Core的框架组件外部访问HttpContext

namespace System.Web
{
    public static class HttpContext
    {
        private static IHttpContextAccessor _contextAccessor;

        public static Microsoft.AspNetCore.Http.HttpContext Current => _contextAccessor.HttpContext;

        internal static void Configure(IHttpContextAccessor contextAccessor)
        {
            _contextAccessor = contextAccessor;
        }
    }
}

然后：

public static class StaticHttpContextExtensions
{
    public static void AddHttpContextAccessor(this IServiceCollection services)
    {
        services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
    }

    public static IApplicationBuilder UseStaticHttpContext(this IApplicationBuilder app)
    {
        var httpContextAccessor = app.ApplicationServices.GetRequiredService<IHttpContextAccessor>();
        System.Web.HttpContext.Configure(httpContextAccessor);
        return app;
    }
}

然后：

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddHttpContextAccessor();
    }

    public void Configure(IApplicationBuilder app)
    {
        app.UseStaticHttpContext();
        app.UseMvc();
    }
}

您可以像这样使用它：

using System.Web;

public class MyService
{
   public void DoWork()
   {
    var context = HttpContext.Current;
    // continue with context instance
   }
}

在启动中

services.AddHttpContextAccessor();

在控制器中

public class HomeController : Controller
    {
        private readonly IHttpContextAccessor _context;

        public HomeController(IHttpContextAccessor context)
        {
            _context = context; 
        }
        public IActionResult Index()
        {
           var context = _context.HttpContext.Request.Headers.ToList();
           return View();
        }
   }