在.NET Core中将视图返回为字符串

Question

在.NET Core中将视图返回为字符串

Has*_*sef 53 c# asp.net razor .net-core asp.net-core

我发现了一些文章如何在ASP.NET中将视图返回到字符串,但无法转换为能够使用.NET Core运行它

public static string RenderViewToString(this Controller controller, string viewName, object model)
{
    var context = controller.ControllerContext;
    if (string.IsNullOrEmpty(viewName))
        viewName = context.RouteData.GetRequiredString("action");

    var viewData = new ViewDataDictionary(model);

    using (var sw = new StringWriter())
    {
        var viewResult = ViewEngines.Engines.FindPartialView(context, viewName);
        var viewContext = new ViewContext(context, viewResult.View, viewData, new TempDataDictionary(), sw);
        viewResult.View.Render(viewContext, sw);

        return sw.GetStringBuilder().ToString();
    }
}

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假设能够使用以下控制器从控制器调用:

var strView = this.RenderViewToString("YourViewName", yourModel);

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当我尝试将上述内容运行到.NET Core时,我遇到了很多编译错误.

我试图将其转换为使用.NET Core,但失败了,任何人都可以帮助提及所需的using ..和所需"dependencies": { "Microsoft.AspNetCore.Mvc": "1.1.0", ... },的project.json.

其他一些示例代码在这里,这里和这里

注意我需要解决方案来将视图转换为string.NET Core,无论相同的代码是否被转换,或者其他方式可以做到.

Answer 1

Red*_*Red 69

如果像我一样,你有许多需要这个的控制器,比如在报告网站中,重复这段代码并不是很理想,甚至注入或调用另一个服务似乎并不合适.

所以我已经制作了我自己的上述版本,但有以下不同之处:

模型强类型
查找视图时的错误检查
将视图呈现为部分或页面的能力
asynchronus
实现为控制器扩展

不需要DI

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System.IO;
using System.Threading.Tasks;

namespace CC.Web.Helpers
{
    public static class ControllerExtensions
    {
        public static async Task<string> RenderViewAsync<TModel>(this Controller controller, string viewName, TModel model, bool partial = false)
        {
            if (string.IsNullOrEmpty(viewName))
            {
                viewName = controller.ControllerContext.ActionDescriptor.ActionName;
            }

            controller.ViewData.Model = model;

            using (var writer = new StringWriter())
            {
                IViewEngine viewEngine = controller.HttpContext.RequestServices.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;
                ViewEngineResult viewResult = viewEngine.FindView(controller.ControllerContext, viewName, !partial);

                if (viewResult.Success == false)
                {
                    return $"A view with the name {viewName} could not be found";
                }

                ViewContext viewContext = new ViewContext(
                    controller.ControllerContext,
                    viewResult.View,
                    controller.ViewData,
                    controller.TempData,
                    writer,
                    new HtmlHelperOptions()
                );

                await viewResult.View.RenderAsync(viewContext);

                return writer.GetStringBuilder().ToString();
            }
        }
    }
}

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然后执行:

viewHtml = await this.RenderViewAsync("Report", model);

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或者这对于PartialView:

partialViewHtml = await this.RenderViewAsync("Report", model, true);

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这应该是更多的方式.它看起来更优雅,它对我来说就像一个魅力. (9认同)
如果找不到视图，我宁愿抛出异常，而不是得到令人惊讶的结果：`return $"A view with the name {viewName} Could not be find";` (3认同)
谢谢,优秀的解决方案我唯一改变的是为部分视图添加一个额外的包装扩展方法.我在使用之前注入的ViewRenderService时遇到了一些问题,因为它可以从其他控制器的视图树访问部分视图.这些视图确实正确呈现,但在调试期间永远不会自动重新编译,将它们移动到共享视图解决了问题! (2认同)
如果您的视图位于不寻常的位置，则此方法不起作用。我在自己的答案中发布了修复程序。 (2认同)
这是在服务器上运行的，因此不会执行客户端代码。如果您无法重构以使用模型数据，我认为您不走运 (2认同)

Answer 2

Has*_*sef 42

感谢Paris Polyzos和他的文章.

我在这里重新发布他的代码,以防原始帖子因任何原因被删除.

Service在文件中创建viewToString.cs如下代码:

using System;
using System.IO;
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.Routing;
 
namespace WebApplication.Services
{
    public interface IViewRenderService
    {
        Task<string> RenderToStringAsync(string viewName, object model);
    }
 
    public class ViewRenderService : IViewRenderService
    {
        private readonly IRazorViewEngine _razorViewEngine;
        private readonly ITempDataProvider _tempDataProvider;
        private readonly IServiceProvider _serviceProvider;
 
        public ViewRenderService(IRazorViewEngine razorViewEngine,
            ITempDataProvider tempDataProvider,
            IServiceProvider serviceProvider)
        {
            _razorViewEngine = razorViewEngine;
            _tempDataProvider = tempDataProvider;
            _serviceProvider = serviceProvider;
        }
 
        public async Task<string> RenderToStringAsync(string viewName, object model)
        {
            var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
            var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
 
            using (var sw = new StringWriter())
            {
                var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);
 
                if (viewResult.View == null)
                {
                    throw new ArgumentNullException($"{viewName} does not match any available view");
                }
 
                var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary())
                {
                    Model = model
                };
 
                var viewContext = new ViewContext(
                    actionContext,
                    viewResult.View,
                    viewDictionary,
                    new TempDataDictionary(actionContext.HttpContext, _tempDataProvider),
                    sw,
                    new HtmlHelperOptions()
                );
 
                await viewResult.View.RenderAsync(viewContext);
                return sw.ToString();
            }
        }
    }
}

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将服务添加到Startup.cs文件中,如下所示:

using WebApplication.Services;

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.AddScoped<IViewRenderService, ViewRenderService>();
 }

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添加"preserveCompilationContext": true到buildOptions中project.json,所以文件看起来像:

{
  "version": "1.0.0-*",
  "buildOptions": {
    "debugType": "portable",
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },
  "dependencies": {
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
    "Microsoft.AspNetCore.Mvc": "1.0.1"
  },
  "frameworks": {
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.0.1"
        }
      },
      "imports": "dnxcore50"
    }
  }
}

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定义你model,例如:

public class InviteViewModel {
    public string   UserId {get; set;}
    public string   UserName {get; set;}
    public string   ReferralCode {get; set;}
    public int  Credits {get; set;}
}

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创建你Invite.cshtml的例子:

@{
    ViewData["Title"] = "Contact";
}
@ViewData["Title"].
user id: @Model.UserId

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在Controller:

一个.在开头定义以下内容:

private readonly IViewRenderService _viewRenderService;
 
public RenderController(IViewRenderService viewRenderService)
{
    _viewRenderService = viewRenderService;
}

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湾使用模型调用并返回视图,如下所示:

var result = await _viewRenderService.RenderToStringAsync("Email/Invite", viewModel);
return Content(result);

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C.完整的控制器示例,可能是:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

using WebApplication.Services;

namespace WebApplication.Controllers
{
[Route("render")]
public class RenderController : Controller
{
    private readonly IViewRenderService _viewRenderService;
 
    public RenderController(IViewRenderService viewRenderService)
    {
        _viewRenderService = viewRenderService;
    }
 
    [Route("invite")]
    public async Task<IActionResult> RenderInviteView()
    {
        ViewData["Message"] = "Your application description page.";
        var viewModel = new InviteViewModel
        {
            UserId = "cdb86aea-e3d6-4fdd-9b7f-55e12b710f78",
            UserName = "Hasan",
            ReferralCode = "55e12b710f78",
            Credits = 10
        };
 
        var result = await _viewRenderService.RenderToStringAsync("Email/Invite", viewModel);
        return Content(result);
    }
}

public class InviteViewModel {
        public string   UserId {get; set;}
        public string   UserName {get; set;}
        public string   ReferralCode {get; set;}
        public int  Credits {get; set;}
} 
}

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这几乎适用于Core 2.0,但有两个例外:(1)_razorViewEngine.FindView在绝对路径上不起作用,我至少需要这些,因为标准模板应用程序不使用它假定的Views文件夹.Tto使用他在Core 2.0 GitHub站点上被记录为"按设计",解决方案是使用_razorViewEngine.GetView,它支持绝对路径.(2)没有解释preserveCompilationContext(不在原文中) - 为什么需要它？目前尚不清楚在哪里使用COre 2.0,它似乎没有它. (11认同)
使用此代码ViewData ["Message"] ="您的应用程序描述页面."; 在视图中将为null.为什么？任何人都可以发布一个包含正确处理ViewData的固定版本,而不仅仅是视图模型. (2认同)

Answer 3

HMZ*_*HMZ 23

ASP.NET 核心 3.1

我知道这里有很多好的答案，我想我也分享我的：

这是从 GitHub 上的 asp.net core 的源代码中提取的，我通常使用它来使用 Razor 呈现 HTML 电子邮件以及通过 Ajax 或 SignalR 返回部分视图的 HTML。

添加为瞬态服务并在控制器中注入 DI

    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.ViewEngines;
    using Microsoft.AspNetCore.Mvc.ViewFeatures;
    using Microsoft.AspNetCore.Routing;
    using System;
    using System.IO;
    using System.Linq;
    using System.Threading.Tasks;

    public sealed class RazorViewToStringRenderer : IRazorViewToStringRenderer
    {
        private readonly IRazorViewEngine _viewEngine;
        private readonly ITempDataProvider _tempDataProvider;
        private readonly IServiceProvider _serviceProvider;

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

        public async Task<string> RenderViewToStringAsync<TModel>(string viewName, TModel model)
        {
           //If you wish to use the route data in the generated view (e.g. use 
           //the Url helper to construct dynamic links)
           //inject the IHttpContextAccessor then use: var actionContext = new ActionContext(_contextAccessor.HttpContext, _contextAccessor.HttpContext.GetRouteData(), new ActionDescriptor());
          //instead of the line below

            var actionContext = GetActionContext();
            var view = FindView(actionContext, viewName);

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

                await view.RenderAsync(viewContext);

                return output.ToString();
            }
        }

        private IView FindView(ActionContext actionContext, string viewName)
        {
            var getViewResult = _viewEngine.GetView(executingFilePath: null, viewPath: viewName, isMainPage: true);
            if (getViewResult.Success)
            {
                return getViewResult.View;
            }

            var findViewResult = _viewEngine.FindView(actionContext, viewName, isMainPage: true);
            if (findViewResult.Success)
            {
                return findViewResult.View;
            }

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

            throw new InvalidOperationException(errorMessage);
        }

        private ActionContext GetActionContext()
        {
            var httpContext = new DefaultHttpContext();
            httpContext.RequestServices = _serviceProvider;
            return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
        }
    }

    public interface IRazorViewToStringRenderer
    {
        Task<string> RenderViewToStringAsync<TModel>(string viewName, TModel model);
    }

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可悲的是，这个评论对我来说只说了一半。虽然此代码实际完成了将 razor 页面转换为 html 字符串的工作，但周围的设置必须适合，否则编译器会抱怨。确保将 `services.AddControllersWithViews();` 和 `services.AddRazorPages();` 添加到 Startup.cs 中。确保在下面正确添加 DI：`services.AddTransient<IRazorViewToStringRenderer, RazorViewToStringRenderer>();` 并确保您的项目位于 .Net Core 3.1 上。我感觉这在 .net core 3 上工作有问题。如果我错了，请纠正我。希望这对一些人有帮助1 (2认同)

Answer 4

Pha*_*lon 10

Red的回答使我有99％的解决方法，但是如果您的视图位于意外位置，则无法使用。这是我的解决办法。

using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System.IO;
using System.Threading.Tasks;

namespace Example
{
    public static class ControllerExtensions
    {
        public static async Task<string> RenderViewAsync<TModel>(this Controller controller, string viewName, TModel model, bool isPartial = false)
        {
            if (string.IsNullOrEmpty(viewName))
            {
                viewName = controller.ControllerContext.ActionDescriptor.ActionName;
            }

            controller.ViewData.Model = model;

            using (var writer = new StringWriter())
            {
                IViewEngine viewEngine = controller.HttpContext.RequestServices.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;
                ViewEngineResult viewResult = GetViewEngineResult(controller, viewName, isPartial, viewEngine);

                if (viewResult.Success == false)
                {
                    throw new System.Exception($"A view with the name {viewName} could not be found");
                }

                ViewContext viewContext = new ViewContext(
                    controller.ControllerContext,
                    viewResult.View,
                    controller.ViewData,
                    controller.TempData,
                    writer,
                    new HtmlHelperOptions()
                );

                await viewResult.View.RenderAsync(viewContext);

                return writer.GetStringBuilder().ToString();
            }
        }

        private static ViewEngineResult GetViewEngineResult(Controller controller, string viewName, bool isPartial, IViewEngine viewEngine)
        {
            if (viewName.StartsWith("~/"))
            {
                var hostingEnv = controller.HttpContext.RequestServices.GetService(typeof(IHostingEnvironment)) as IHostingEnvironment;
                return viewEngine.GetView(hostingEnv.WebRootPath, viewName, !isPartial);
            }
            else
            {
                return viewEngine.FindView(controller.ControllerContext, viewName, !isPartial);

            }
        }
    }
}

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这使您可以如下使用它：

var emailBody = await this.RenderViewAsync("~/My/Different/View.cshtml", myModel);

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有效，但“IHostingEnvironment”已过时。只需替换为“IWebHostEnvironment”即可。 (4认同)
这个答案有一个问题，因为它改变了控制器自己的模型“controller.ViewData.Model = model;”，我们必须撤消任何更改，否则会破坏后续视图渲染。我将这个突变和渲染封装在 try-finally 中来修复它。 (3认同)

Answer 5

Mah*_*san 10

.NET 5

这里已经发布了很多很棒的答案。基本上我遇到了类似的问题，我想从 razor (.cshtml) 页面读取电子邮件模板作为字符串，我遇到了这个问题并尝试了所有答案。我在 .NET 5 中遇到了一些问题，因此我在这里发布了稍微调整过的解决方案。谢谢。

Startup.cs文件

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.AddScoped<CustomViewRendererService>();
    ...
}

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CustomViewRendererService.cs文件

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System;
using System.IO;
using System.Threading.Tasks;

namespace Services
{
    public class CustomViewRendererService
    {
        private readonly IRazorViewEngine _razorViewEngine;
        private readonly ITempDataProvider _tempDataProvider;

        public CustomViewRendererService(
            IRazorViewEngine razorViewEngine,
            ITempDataProvider tempDataProvider)
        {
            _razorViewEngine = razorViewEngine;
            _tempDataProvider = tempDataProvider;
        }
        
        public async Task<string> RenderViewToStringAsync(ControllerContext actionContext, string viewPath, object model)
        {
            var viewEngineResult = _razorViewEngine.GetView(viewPath, viewPath, false);

            if (viewEngineResult.View == null || (!viewEngineResult.Success))
            {
                throw new ArgumentNullException($"Unable to find view '{viewPath}'");
            }

            var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), actionContext.ModelState);
            viewDictionary.Model = model;

            var view = viewEngineResult.View;
            var tempData = new TempDataDictionary(actionContext.HttpContext, _tempDataProvider);

            using var sw = new StringWriter();
            var viewContext = new ViewContext(actionContext, view, viewDictionary, tempData, sw, new HtmlHelperOptions());
            await view.RenderAsync(viewContext);
            return sw.ToString();
        }
    }
}

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在我的控制器中

public class TestController : ControllerBase
{
    private readonly CustomViewRendererService _viewService;

    public TestController(CustomViewRendererService viewService)
    {
        _viewService = viewService;
    }

    public async Task<IActionResult> SendTestEmail2Async()
    {
        var templatePath = "~/Views/Email/Test.cshtml";
        var msg = await _viewService.RenderViewToStringAsync(ControllerContext, templatePath, ("Foo", "Bar"));
        
        return Ok(msg);
    }
}

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最后Test.cshtml归档

@model (string arg1, string arg2)

<h1>Param: @Model.arg1</h1>
<h1>Param @Model.arg2</h1>

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Answer 6

Dav*_*row 5

上面的答案很好，但需要进行调整才能使任何标签助手工作（我们需要使用实际的 http 上下文）。此外，您还需要在视图中显式设置布局才能呈现布局。

public class ViewRenderService : IViewRenderService
{
    private readonly IRazorViewEngine _razorViewEngine;
    private readonly ITempDataProvider _tempDataProvider;
    private readonly IServiceProvider _serviceProvider;
    private readonly IHostingEnvironment _env;
    private readonly HttpContext _http;

    public ViewRenderService(IRazorViewEngine razorViewEngine, ITempDataProvider tempDataProvider, IServiceProvider serviceProvider, IHostingEnvironment env, IHttpContextAccessor ctx)
    {
        _razorViewEngine = razorViewEngine; _tempDataProvider = tempDataProvider; _serviceProvider = serviceProvider; _env = env; _http = ctx.HttpContext;
    }

    public async Task<string> RenderToStringAsync(string viewName, object model)
    {
        var actionContext = new ActionContext(_http, new RouteData(), new ActionDescriptor());

        using (var sw = new StringWriter())
        {
            var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);
            //var viewResult = _razorViewEngine.GetView(_env.WebRootPath, viewName, false); // For views outside the usual Views folder
            if (viewResult.View == null)
            {
                throw new ArgumentNullException($"{viewName} does not match any available view");
            }
            var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary())
            {
                Model = model
            };
            var viewContext = new ViewContext(actionContext, viewResult.View, viewDictionary, new TempDataDictionary(_http, _tempDataProvider), sw, new HtmlHelperOptions());
            viewContext.RouteData = _http.GetRouteData();
            await viewResult.View.RenderAsync(viewContext);
            return sw.ToString();
        }
    }
}

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注意：在 azure 上，我需要将以下内容添加到 Startup `services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>(); ` 在没有这个的情况下，在本地工作得很好...... (2认同)

Answer 7

Mla*_* B. 5

我可能迟到了，但我设法找到了一种解决方案，该解决方案无需实例化新的视图引擎( RazorViewEngine )，而是实际重用每个控制器中已有的视图引擎。此外，通过这种方法，我们还可以在键入视图名称时从IntelliSense获得帮助，这在尝试确定确切的视图路径时非常有用。

因此，使用这种方法，您的代码将如下所示：

public override async Task<IActionResult> SignUp()
{
    ...
    // send an email notification
    var emailView = View("Emails/SignupNotification"); // simply get the email view
    var emailBody = await RenderToStringAsync(emailView, _serviceProvider); // render it as a string

    SendEmail(emailBody);
    ...

    return View();
}

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RenderToStringAsync本示例中使用的方法如下所示：

private static async Task<string> RenderToStringAsync(ViewResult viewResult, IServiceProvider serviceProvider)
{
    if (viewResult == null) throw new ArgumentNullException(nameof(viewResult));

    var httpContext = new DefaultHttpContext
    {
        RequestServices = serviceProvider
    };

    var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());

    using (var stream = new MemoryStream())
    {
        httpContext.Response.Body = stream; // inject a convenient memory stream
        await viewResult.ExecuteResultAsync(actionContext); // execute view result on that stream

        httpContext.Response.Body.Position = 0;
        return new StreamReader(httpContext.Response.Body).ReadToEnd(); // collect the content of the stream
    }
}

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如果您将该方法实现为扩展方法，则您的用法可以变成：

public override async Task<IActionResult> SignUp()
{
    ...
    var emailBody = View("Emails/SignupNotification")
        .RenderToStringAsync(_serviceProvider);
    ...

    return View();
}

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