首页 文章

将Razor页面渲染为字符串

提问于
浏览 次
10

问题：

我需要将Razor页面部分渲染为字符串 .

为什么我要这个：

我想创建一个控制器操作，该操作使用包含部分视图和其他可选参数的JSON进行响应 .

尝试：

我熟悉以下将View呈现为字符串的示例：https://github.com/aspnet/Entropy/blob/dev/samples/Mvc.RenderViewToString/RazorViewToStringRenderer.cs

但是，它与Pages不兼容，因为它只在Views目录中搜索，所以即使我给它一个绝对的路径，它试图找到我的_Layout.cshtml（它甚至不应该这样做！）并失败找到它 .

我试图修改它以便渲染页面，但是在尝试渲染时，我最终在部分中获得了ViewData的NullReferenceException . 我怀疑它与NullView有关，但我不知道该放在那里（RazorView的构造函数需要许多我不知道如何正确获取的对象） .

代码：

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0: https://www.apache.org/licenses/LICENSE-2.0
// Modified by OronDF343: Uses pages instead of views.

using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
using Microsoft.AspNetCore.Routing;

namespace TestAspNetCore.Services
{
    public class RazorPageToStringRenderer
    {
        private readonly IRazorViewEngine _viewEngine;
        private readonly ITempDataProvider _tempDataProvider;
        private readonly IServiceProvider _serviceProvider;

        public RazorPageToStringRenderer(
            IRazorViewEngine viewEngine,
            ITempDataProvider tempDataProvider,
            IServiceProvider serviceProvider)
        {
            _viewEngine = viewEngine;
            _tempDataProvider = tempDataProvider;
            _serviceProvider = serviceProvider;
        }

        public async Task<string> RenderPageToStringAsync<TModel>(string viewName, TModel model)
        {
            var actionContext = GetActionContext();
            var page = FindPage(actionContext, viewName);

            using (var output = new StringWriter())
            {
                var viewContext = new ViewContext(actionContext,
                                                  new NullView(),
                                                  new ViewDataDictionary<TModel>(new EmptyModelMetadataProvider(),
                                                                                 new ModelStateDictionary())
                                                  {
                                                      Model = model
                                                  },
                                                  new TempDataDictionary(actionContext.HttpContext,
                                                                         _tempDataProvider),
                                                  output,
                                                  new HtmlHelperOptions());

                page.ViewContext = viewContext;
                await page.ExecuteAsync();

                return output.ToString();
            }
        }

        private IRazorPage FindPage(ActionContext actionContext, string pageName)
        {
            var getPageResult = _viewEngine.GetPage(executingFilePath: null, pagePath: pageName);
            if (getPageResult.Page != null)
            {
                return getPageResult.Page;
            }

            var findPageResult = _viewEngine.FindPage(actionContext, pageName);
            if (findPageResult.Page != null)
            {
                return findPageResult.Page;
            }

            var searchedLocations = getPageResult.SearchedLocations.Concat(findPageResult.SearchedLocations);
            var errorMessage = string.Join(
                Environment.NewLine,
                new[] { $"Unable to find page '{pageName}'. The following locations were searched:" }.Concat(searchedLocations));

            throw new InvalidOperationException(errorMessage);
        }

        private ActionContext GetActionContext()
        {
            var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
            return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
        }
    }
}
c# razor asp.net-core asp.net-core-2.0 razor-pages

2 回答

  • 2

    这就是我做到的 .

    始终在Startup.cs中注册服务

    services.AddScoped<IViewRenderService, ViewRenderService>();

    该服务定义如下：

    public interface IViewRenderService
{
    Task<string> RenderToStringAsync<T>(string viewName, T model) where T : PageModel;
}

public class ViewRenderService : IViewRenderService
{
    private readonly IRazorViewEngine _razorViewEngine;
    private readonly ITempDataProvider _tempDataProvider;
    private readonly IServiceProvider _serviceProvider;
    private readonly IHttpContextAccessor _httpContext;
    private readonly IActionContextAccessor _actionContext;
    private readonly IRazorPageActivator _activator;


    public ViewRenderService(IRazorViewEngine razorViewEngine,
        ITempDataProvider tempDataProvider,
        IServiceProvider serviceProvider,
        IHttpContextAccessor httpContext,
        IRazorPageActivator activator,
        IActionContextAccessor actionContext)
    {
        _razorViewEngine = razorViewEngine;
        _tempDataProvider = tempDataProvider;
        _serviceProvider = serviceProvider;

        _httpContext = httpContext;
        _actionContext = actionContext;
        _activator = activator;

    }


    public async Task<string> RenderToStringAsync<T>(string pageName, T model) where T : PageModel
    {


        var actionContext =
            new ActionContext(
                _httpContext.HttpContext,
                _httpContext.HttpContext.GetRouteData(),
                _actionContext.ActionContext.ActionDescriptor
            );

        using (var sw = new StringWriter())
        {
            var result = _razorViewEngine.FindPage(actionContext, pageName);

            if (result.Page == null)
            {
                throw new ArgumentNullException($"The page {pageName} cannot be found.");
            }

            var view = new RazorView(_razorViewEngine,
                _activator,
                new List<IRazorPage>(),
                result.Page,
                HtmlEncoder.Default,
                new DiagnosticListener("ViewRenderService"));


            var viewContext = new ViewContext(
                actionContext,
                view,
                new ViewDataDictionary<T>(new EmptyModelMetadataProvider(), new ModelStateDictionary())
                {
                    Model = model
                },
                new TempDataDictionary(
                    _httpContext.HttpContext,
                    _tempDataProvider
                ),
                sw,
                new HtmlHelperOptions()
            );


            var page = ((Page)result.Page);

            page.PageContext = new Microsoft.AspNetCore.Mvc.RazorPages.PageContext
            {
                ViewData = viewContext.ViewData

            };

            page.ViewContext = viewContext;


            _activator.Activate(page, viewContext);

            await page.ExecuteAsync();


            return sw.ToString();
        }
    }



}

    我这样称呼它

    emailView.Body = await this._viewRenderService.RenderToStringAsync("Email/ConfirmAccount", new Email.ConfirmAccountModel
                {
                    EmailView = emailView,
                });

    “Email / ConfirmAccount”是我的Razor页面的路径（在页面下） . “ConfirmAccountModel”是该页面的页面模型 .

    ViewData为null，因为在设置PageContext时设置了Page的ViewData，因此如果未设置，则ViewData为null .

    我还发现我不得不打电话

    _activator.Activate(page, viewContext);

    为了这一切工作 . 这尚未经过全面测试，因此可能无法适用于所有场景，但应该可以帮助您入门 .

    回复于
  • 6

    我有同样的问题 .

    我查看了RazorViewEngine源代码，发现使用“page”路由数据搜索页面：

    var routeData = new RouteData();
routeData.Values.Add("page", "/Folder/MyPage");

    这对我来说是路径数据中的完整路径“/ Folder / MyPage”，以及GetPage调用中的页面名称“MyPage” .

    回复于

相关问题