Asp.Net Core 中的 @Html.Action [英] @Html.Action in Asp.Net Core

问题描述

@Html.Action 在 Asp.net Core 中的什么位置?我可以看到 @Html.ActionLink 但不能像以前那样直接调用 Action.

Where is @Html.Action in Asp.net Core? I can see @Html.ActionLink but not a direct call to an Action as before.

是不是被 ViewComponents 取代了?

Was it replaced by ViewComponents?

推荐答案

更新:从 2.2.2 HttpContextAccessor 开始，将上下文保存在一个对象中(据说是为了防止内部请求混淆)，它会影响当前的解决方案......所以您需要为 IHttpContextAccessor(旧版本)提供以下实现并将其注册为单例:

Update: As of 2.2.2 HttpContextAccessor keep the context in an object (supposedly to prevent inter request mix up) and it impacts the current solution... So you need to provide the following implementation for IHttpContextAccessor (an old version) and register it as a singleton:

public class HttpContextAccessor : IHttpContextAccessor
{
    private static AsyncLocal<HttpContext> _httpContextCurrent = new AsyncLocal<HttpContext>();
    HttpContext IHttpContextAccessor.HttpContext { get => _httpContextCurrent.Value; set => _httpContextCurrent.Value = value; }
}

<小时>

对于asp.net core 2

---

For asp.net core 2

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<IHtmlContent> 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<IActionContextAccessor>();
            var httpContextAccessor = helper.ViewContext.HttpContext.RequestServices.GetRequiredService<IHttpContextAccessor>();
            var actionSelector = serviceProvider.GetRequiredService<IActionSelector>();

            // 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<IHttpContextFactory>().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<IActionInvokerFactory>().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));
                }
            }
        }
    }
}

它基于白羊座的反应.我更正了没有为 2.0 编译的内容，并添加了一些调整.当前的 httpcontext 和当前的 actioncontext 有 2 个美化的静态值.httpcontext 的一个在 IHttpContextFactory.Create 中设置，我在代码中为 actioncontext 设置了一个.请注意，根据您使用的功能，IActionContextAccessor 和 IHttpContextAccessor 可能默认未注册，因此您可能需要在启动时添加它们:

It is based on Aries response. I corrected what wasn't compiling for 2.0 and I added a couple of tweaks. There are 2 glorified static values for the current httpcontext and the current actioncontext. The one for httpcontext is set in IHttpContextFactory.Create and I set the one for actioncontext in the code. Note that depending on the features you use IActionContextAccessor and IHttpContextAccessor may not be registered by default, so you may need to add them in your startup:

services.AddSingleton();services.AddSingleton();

HttpContext 只是 HttpContext.Features 的一个包装器，所以如果你改变了一个东西，它也会改变另一个......我在 try/的最后重置了我所知道的抓住.

HttpContext is just a wrapper around HttpContext.Features, so if you change something in one, it also changes in the other... I reset what I know about in the finally of the try/catch.

我从项目缓存中删除了 IUrlHelper，因为即使构建 urlHelper 的 actionContext 不同(IUrlHelperFactory.GetUrlHelper)，这个值也会被重用.

I removed the IUrlHelper from the Items cache since this value will be reused even if the actionContext to build the urlHelper is different(IUrlHelperFactory.GetUrlHelper).

Asp.net core 2.0 假设你不会这样做，很有可能还有其他缓存的东西，所以我建议在使用它时要小心，如果你不需要就不要.

Asp.net core 2.0 assumes you won't do this, there is a good chance there are other cached things, so I recommend to be careful when using this and just don't if you don't need to.

这篇关于Asp.Net Core 中的 @Html.Action的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！