ASP.NET 的Request 物件的生命周期很短，只会出现在一个Http Request，当需要跨物件传递资料时，比如HttpModule、HttpHandler、Page 、Controller，可以善用Request 物件来存放短暂的状态。
既然可以传递物件，那么我们也可以在Request 初始化的时候，将所需要的物件注入至Request 里面，然后再到到Page / Controller 取出来用；在不同的专案范本可以使用的Request 物件都不太一样，接下来分享我已经知道的写法。
开发环境
VS IDE 2019
IIS主机ASP.NET 4.8 WebForm / MVC5 / Web API
OWIN主机Web API
ASP.NET Core 3.1
存放状态的方式是key-value，型别为IDictionary or IDictionary
System.Web.HttpContext.Items
.NET 2.0的时代用HttpContext.Items (IDictionary Type)，到了.NET 3.5之后可以改用HttpContextBase.Items。
HttpContextWrapper则是用来把HttpContext变成HttpContextBase。
HttpContextBase是一个抽象，可以让我们更好测试 [Unit Test]使用HttpContextBase取代HttpContext.Current，提高可测试性
HttpContext.Items 是IDictionary型别，Key对应Object。
适用ASP.NET WebForm、ASP.NET MVC。
从Global.asax注入Member物件至 HttpContext.Items
重庆分公司
重庆分公司
public class Global : HttpApplication{ protected void Application_BeginRequest()
{
var member = new Member {Id = Guid.NewGuid(), Name = Name.FullName()};
var key = member.GetType().FullName; HttpContext.Current.Items[key] = member; }}
在Default.aspx.cs取出，这里我用了HttpContextWrapper把HttpContext转成HttpContextBase
public partial class Default : Page{ protected void Page_Load(object sender, EventArgs e)
{
if (this.IsPostBack) { return; }
var httpContext = new HttpContextWrapper(HttpContext.Current);
var key = typeof(Member).FullName;
var member = httpContext.Items[key] as Member;
this.Id_Label.Text = member.Id.ToString();
this.Name_Label.Text = member.Name; }}
System.Web.HttpContextBase.Items
Controller 依赖HttpContextBase 非HttpContext
适用ASP.NET MVC5
在 ActionFilterAttribute 注入 Member 物件至 HttpContextBase.Items
public class InjectionAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
//初始化物件
var member = new Member {Id = Guid.NewGuid(), Name =Faker.Name.FullName()};
var key = member.GetType().FullName;
//注入到 HttpContextBase
filterContext.RequestContext.HttpContext.Items[key] = member;
}
}
在 Controller 取出 Member 物件
public class HomeController : Controller
{
// GET: Default
public ActionResult Index()
{
var key = typeof(Member).FullName;
var member = this.HttpContext.Items[key];
return View(member);
}
}
System.Net.Http.HttpRequestMessage.Properties
HttpRequestMessage.Properties [“ key”] 是IDictionary
适用的ASP.NET Web API / ASP.NET Core Web API
在 ActionFilterAttribute 注入 Member 物件至 HttpRequestMessage.Properties["key"]
public class InjectionAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext filterContext)
{
//初始化物件
var member = new Member {Id = Guid.NewGuid(), Name = Faker.Name.FullName()};
var key = member.GetType().FullName;
//注入到 HttpRequestMessage
filterContext.Request.Properties[key] = member;
}
}
在 ApiController 取出 Member 物件
public class DefaultController : ApiController
{
// GET: api/Default
public IHttpActionResult Get()
{
var key = typeof(Member).FullName;
var member = this.Request.Properties[key] as Member;
return this.Ok(member);
}
}
Microsoft.Owin.IOwinContext.Environment
IOwinContext.Environment 是IDictionary
IOwinContext.Set/Get骨子里面是控制IOwinContext.Environment
适用OWIN
app.Use Middleware 注入 Member 物件至 IOwinContext.Environment["key"]
public class Startup
{
public void Configuration(IAppBuilder app)
{
var config = new HttpConfiguration();
// Web API configuration and services
// Web API routes
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute("DefaultApi",
"api/{controller}/{id}",
new {id = RouteParameter.Optional}
);
app.Use(async (owinContext, next) =>
{
var member = new Member
{
Id = Guid.NewGuid(),
Name = Name.FullName()
};
//owinContext.Set(member.GetType().FullName, member);
owinContext.Environment[member.GetType().FullName] = member;
await next();
});
app.UseErrorPage()
.UseWebApi(config);
}
}
在 ApiController ，用 IOwinContext.Get 取出 Member 物件
public class DefaultController : ApiController
{
// GET: api/Default
public IHttpActionResult Get()
{
var key = typeof(Member).FullName;
var member = this.Request.GetOwinContext().Get(key);
return this.Ok(member);
}
}
Microsoft.AspNetCore.Http.HttpContext.Items
HttpContext.Items 是IDictionary
适用ASP.NET Core
app.Use Middleware 注入 Member 物件至 HttpContext.Items
public class Startup
{
public IConfiguration Configuration { get; }
public Startup(IConfiguration configuration)
{
this.Configuration = configuration;
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.Use(async (owinContext, next) =>
{
var member = new Member
{
Id = Guid.NewGuid(),
Name = Faker.Name.FullName()
};
var key = member.GetType().FullName;
owinContext.Items[key] = member;
await next();
});
app.UseHttpsRedirection();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
}
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
}
}
在 Controller 用 HttpContext.Items 取出 Member
[ApiController]
[Route("api/[controller]")]
public class DefaultController : ControllerBase
{
[HttpGet]
public async Task> Get()
{
var key = typeof(Member).FullName;
var member = this.HttpContext.Items[key] as Member;
return this.Ok(member);
}
} 
