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Add new Microsoft.AspNetCore.SpaServices.Extensions package to host new runtime functionality needed for updated templates until 2.1 ships
This commit is contained in:
Steve Sanderson
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// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
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using Microsoft.AspNetCore.Hosting;
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using Microsoft.AspNetCore.Http;
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using Microsoft.AspNetCore.Http.Features;
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using Microsoft.AspNetCore.NodeServices;
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using Microsoft.AspNetCore.SpaServices;
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using Microsoft.AspNetCore.SpaServices.Prerendering;
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using Microsoft.Extensions.DependencyInjection;
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using Microsoft.Net.Http.Headers;
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using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace Microsoft.AspNetCore.Builder
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{
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/// <summary>
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/// Extension methods for configuring prerendering of a Single Page Application.
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/// </summary>
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public static class SpaPrerenderingExtensions
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{
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/// <summary>
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/// Enables server-side prerendering middleware for a Single Page Application.
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/// </summary>
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/// <param name="spaBuilder">The <see cref="ISpaBuilder"/>.</param>
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/// <param name="configuration">Supplies configuration for the prerendering middleware.</param>
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public static void UseSpaPrerendering(
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this ISpaBuilder spaBuilder,
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Action<SpaPrerenderingOptions> configuration)
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{
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if (spaBuilder == null)
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{
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throw new ArgumentNullException(nameof(spaBuilder));
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}
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if (configuration == null)
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{
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throw new ArgumentNullException(nameof(configuration));
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}
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var options = new SpaPrerenderingOptions();
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configuration.Invoke(options);
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var capturedBootModulePath = options.BootModulePath;
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if (string.IsNullOrEmpty(capturedBootModulePath))
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{
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throw new InvalidOperationException($"To use {nameof(UseSpaPrerendering)}, you " +
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$"must set a nonempty value on the ${nameof(SpaPrerenderingOptions.BootModulePath)} " +
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$"property on the ${nameof(SpaPrerenderingOptions)}.");
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}
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// If we're building on demand, start that process in the background now
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var buildOnDemandTask = options.BuildOnDemand?.Build(spaBuilder);
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// Get all the necessary context info that will be used for each prerendering call
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var applicationBuilder = spaBuilder.ApplicationBuilder;
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var serviceProvider = applicationBuilder.ApplicationServices;
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var nodeServices = GetNodeServices(serviceProvider);
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var applicationStoppingToken = serviceProvider.GetRequiredService<IApplicationLifetime>()
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.ApplicationStopping;
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var applicationBasePath = serviceProvider.GetRequiredService<IHostingEnvironment>()
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.ContentRootPath;
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var moduleExport = new JavaScriptModuleExport(capturedBootModulePath);
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var excludePathStrings = (options.ExcludeUrls ?? Array.Empty<string>())
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.Select(url => new PathString(url))
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.ToArray();
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applicationBuilder.Use(async (context, next) =>
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{
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// If this URL is excluded, skip prerendering.
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// This is typically used to ensure that static client-side resources
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// (e.g., /dist/*.css) are served normally or through SPA development
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// middleware, and don't return the prerendered index.html page.
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foreach (var excludePathString in excludePathStrings)
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{
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if (context.Request.Path.StartsWithSegments(excludePathString))
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{
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await next();
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return;
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}
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}
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// If we're building on demand, wait for that to finish, or raise any build errors
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if (buildOnDemandTask != null)
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{
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await buildOnDemandTask;
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}
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// It's no good if we try to return a 304. We need to capture the actual
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// HTML content so it can be passed as a template to the prerenderer.
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RemoveConditionalRequestHeaders(context.Request);
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// Capture the non-prerendered responses, which in production will typically only
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// be returning the default SPA index.html page (because other resources will be
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// served statically from disk). We will use this as a template in which to inject
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// the prerendered output.
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using (var outputBuffer = new MemoryStream())
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{
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var originalResponseStream = context.Response.Body;
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context.Response.Body = outputBuffer;
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try
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{
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await next();
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outputBuffer.Seek(0, SeekOrigin.Begin);
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}
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finally
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{
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context.Response.Body = originalResponseStream;
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}
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// If it's not a success response, we're not going to have any template HTML
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// to pass to the prerenderer.
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if (context.Response.StatusCode < 200 || context.Response.StatusCode >= 300)
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{
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var message = $"Prerendering failed because no HTML template could be obtained. " +
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$"Check that your SPA is compiling without errors. " +
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$"The {nameof(SpaApplicationBuilderExtensions.UseSpa)}() middleware returned " +
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$"a response with status code {context.Response.StatusCode}.";
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if (outputBuffer.Length > 0)
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{
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message += " and the following content: "
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+ Encoding.UTF8.GetString(outputBuffer.GetBuffer());
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}
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throw new InvalidOperationException(message);
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}
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// Most prerendering logic will want to know about the original, unprerendered
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// HTML that the client would be getting otherwise. Typically this is used as
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// a template from which the fully prerendered page can be generated.
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var customData = new Dictionary<string, object>
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{
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{ "originalHtml", Encoding.UTF8.GetString(outputBuffer.GetBuffer()) }
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};
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// If the developer wants to use custom logic to pass arbitrary data to the
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// prerendering JS code (e.g., to pass through cookie data), now's their chance
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options.SupplyData?.Invoke(context, customData);
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var (unencodedAbsoluteUrl, unencodedPathAndQuery)
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= GetUnencodedUrlAndPathQuery(context);
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var renderResult = await Prerenderer.RenderToString(
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applicationBasePath,
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nodeServices,
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applicationStoppingToken,
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moduleExport,
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unencodedAbsoluteUrl,
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unencodedPathAndQuery,
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customDataParameter: customData,
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timeoutMilliseconds: 0,
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requestPathBase: context.Request.PathBase.ToString());
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await ServePrerenderResult(context, renderResult);
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}
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});
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}
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private static void RemoveConditionalRequestHeaders(HttpRequest request)
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{
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request.Headers.Remove(HeaderNames.IfMatch);
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request.Headers.Remove(HeaderNames.IfModifiedSince);
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request.Headers.Remove(HeaderNames.IfNoneMatch);
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request.Headers.Remove(HeaderNames.IfUnmodifiedSince);
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request.Headers.Remove(HeaderNames.IfRange);
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}
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private static (string, string) GetUnencodedUrlAndPathQuery(HttpContext httpContext)
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{
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// This is a duplicate of code from Prerenderer.cs in the SpaServices package.
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// Once the SpaServices.Extension package implementation gets merged back into
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// SpaServices, this duplicate can be removed. To remove this, change the code
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// above that calls Prerenderer.RenderToString to use the internal overload
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// that takes an HttpContext instead of a url/path+query pair.
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var requestFeature = httpContext.Features.Get<IHttpRequestFeature>();
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var unencodedPathAndQuery = requestFeature.RawTarget;
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var request = httpContext.Request;
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var unencodedAbsoluteUrl = $"{request.Scheme}://{request.Host}{unencodedPathAndQuery}";
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return (unencodedAbsoluteUrl, unencodedPathAndQuery);
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}
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private static async Task ServePrerenderResult(HttpContext context, RenderToStringResult renderResult)
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{
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context.Response.Clear();
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if (!string.IsNullOrEmpty(renderResult.RedirectUrl))
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{
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context.Response.Redirect(renderResult.RedirectUrl);
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}
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else
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{
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// The Globals property exists for back-compatibility but is meaningless
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// for prerendering that returns complete HTML pages
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if (renderResult.Globals != null)
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{
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throw new InvalidOperationException($"{nameof(renderResult.Globals)} is not " +
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$"supported when prerendering via {nameof(UseSpaPrerendering)}(). Instead, " +
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$"your prerendering logic should return a complete HTML page, in which you " +
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$"embed any information you wish to return to the client.");
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}
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context.Response.ContentType = "text/html";
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await context.Response.WriteAsync(renderResult.Html);
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}
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}
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private static INodeServices GetNodeServices(IServiceProvider serviceProvider)
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{
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// Use the registered instance, or create a new private instance if none is registered
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var instance = (INodeServices)serviceProvider.GetService(typeof(INodeServices));
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return instance ?? NodeServicesFactory.CreateNodeServices(
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new NodeServicesOptions(serviceProvider));
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}
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}
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}
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