小編典典

更新：從2.2.2版本開始，HttpContextAccessor將上下文保留在一個對象中(據說是為了防止請求之間的混淆)，這會影響當前解決方案…因此，您需要為IHttpContextAccessor(舊版本)提供以下實現并進行注冊作為一個單例：

public class HttpContextAccessor : IHttpContextAccessor

{

private static AsyncLocal _httpContextCurrent = new AsyncLocal();

HttpContext IHttpContextAccessor.HttpContext { get => _httpContextCurrent.Value; set => _httpContextCurrent.Value = value; }

}

using Microsoft.AspNetCore.Html;

using Microsoft.AspNetCore.Http;

using Microsoft.AspNetCore.Mvc.Infrastructure;

using Microsoft.AspNetCore.Routing;

using Microsoft.Extensions.DependencyInjection;

using System;

using System.IO;

using System.Threading.Tasks;

namespace Microsoft.AspNetCore.Mvc.Rendering

{

public static class HtmlHelperViewExtensions

{

public static IHtmlContent Action(this IHtmlHelper helper, string action, object parameters = null)

{

var controller = (string)helper.ViewContext.RouteData.Values["controller"];

return Action(helper, action, controller, parameters);

}

public static IHtmlContent Action(this IHtmlHelper helper, string action, string controller, object parameters = null)

{

var area = (string)helper.ViewContext.RouteData.Values["area"];

return Action(helper, action, controller, area, parameters);

}

public static IHtmlContent Action(this IHtmlHelper helper, string action, string controller, string area, object parameters = null)

{

if (action == null)

throw new ArgumentNullException("action");

if (controller == null)

throw new ArgumentNullException("controller");

var task = RenderActionAsync(helper, action, controller, area, parameters);

return task.Result;

}

private static async Task RenderActionAsync(this IHtmlHelper helper, string action, string controller, string area, object parameters = null)

{

// fetching required services for invocation

var serviceProvider = helper.ViewContext.HttpContext.RequestServices;

var actionContextAccessor = helper.ViewContext.HttpContext.RequestServices.GetRequiredService();

var httpContextAccessor = helper.ViewContext.HttpContext.RequestServices.GetRequiredService();

var actionSelector = serviceProvider.GetRequiredService();

// creating new action invocation context

var routeData = new RouteData();

foreach (var router in helper.ViewContext.RouteData.Routers)

{

routeData.PushState(router, null, null);

}

routeData.PushState(null, new RouteValueDictionary(new { controller = controller, action = action, area = area }), null);

routeData.PushState(null, new RouteValueDictionary(parameters ?? new { }), null);

//get the actiondescriptor

RouteContext routeContext = new RouteContext(helper.ViewContext.HttpContext) { RouteData = routeData };

var candidates = actionSelector.SelectCandidates(routeContext);

var actionDescriptor = actionSelector.SelectBestCandidate(routeContext, candidates);

var originalActionContext = actionContextAccessor.ActionContext;

var originalhttpContext = httpContextAccessor.HttpContext;

try

{

var newHttpContext = serviceProvider.GetRequiredService().Create(helper.ViewContext.HttpContext.Features);

if (newHttpContext.Items.ContainsKey(typeof(IUrlHelper)))

{

newHttpContext.Items.Remove(typeof(IUrlHelper));

}

newHttpContext.Response.Body = new MemoryStream();

var actionContext = new ActionContext(newHttpContext, routeData, actionDescriptor);

actionContextAccessor.ActionContext = actionContext;

var invoker = serviceProvider.GetRequiredService().CreateInvoker(actionContext);

await invoker.InvokeAsync();

newHttpContext.Response.Body.Position = 0;

using (var reader = new StreamReader(newHttpContext.Response.Body))

{

return new HtmlString(reader.ReadToEnd());

}

}

catch (Exception ex)

{

return new HtmlString(ex.Message);

}

finally

{

actionContextAccessor.ActionContext = originalActionContext;

httpContextAccessor.HttpContext = originalhttpContext;

if (helper.ViewContext.HttpContext.Items.ContainsKey(typeof(IUrlHelper)))

{

helper.ViewContext.HttpContext.Items.Remove(typeof(IUrlHelper));

}

}

}

}

}

它基于白羊座的反應。我更正了2.0版未編譯的內容，并添加了一些調整。當前的httpcontext和當前的actioncontext有2個美化的靜態值。在httpcontext中IHttpContextFactory.Create設置了一個，在代碼中設置了actioncontext。請注意，這取決于你使用的功能IActionContextAccessor，并IHttpContextAccessor可能不會被默認注冊，所以你可能需要將其添加在啟動：

services.AddSingleton();

services.AddSingleton();

HttpContext只是一個包裝器HttpContext.Features，因此，如果您在其中一個進行更改，則在另一個中也進行更改…我將在try

/ catch的最后部分重設我所了解的內容。

我IUrlHelper從Items緩存中刪除了，因為即使構建urlHelper的actionContext不同，該值也將被重用IUrlHelperFactory.GetUrlHelper。

Asp.net Core 2.0假設您不會這樣做，那么很有可能還有其他緩存的東西，因此我建議在使用此方法時要格外小心，如果不需要，請不要這樣做。

2020-05-19