Asp.Net Core中的@ Html.Action

  • Z时代
  • 2024-01-10
  • 分类：问答

@Html.ActionAsp.net Core 在哪里？我可以看到@Html.ActionLink但不能像以前一样直接调用Action。

它被ViewComponents取代了吗？

回答：

更新：从2.2.2版本开始，HttpContextAccessor将上下文保留在一个对象中（据说是为了防止请求之间的混淆），这会影响当前解决方案…因此，您需要为IHttpContextAccessor（旧版本）提供以下实现并进行注册作为一个单例：

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

对于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2.0版未编译的内容，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。在httpcontext中IHttpContextFactory.Create设置了一个，在代码中设置了actioncontext。请注意，这取决于你使用的功能IActionContextAccessor，并IHttpContextAccessor可能不会被默认注册，所以你可能需要将其添加在启动：

services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

HttpContext只是一个包装器HttpContext.Features，因此，如果您在其中一个进行更改，则在另一个中也进行更改…我将在try

/ catch的最后部分重设我所了解的内容。

我IUrlHelper从Items缓存中删除了，因为即使构建urlHelper的actionContext不同，该值也将被重用IUrlHelperFactory.GetUrlHelper。

Asp.net Core 2.0假设您不会这样做，那么很有可能还有其他缓存的东西，因此我建议在使用此方法时要格外小心，如果不需要，请不要这样做。

以上是 Asp.Net Core中的@ Html.Action 的全部内容， 来源链接： utcz.com/qa/431234.html

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