从AspNetCore TestHost运行时编译Razor时出现CompilationFailedException

Question

我有ASP.Net MVC应用程序，其中一部分是将剃刀视图编译为字符串。代码与此示例非常相似：https://long2know.com/2017/08/rendering-and-emailing-embedded-razor-views-with-net-core/

我以这种方式在Startup.cs注册了Razor引擎：

var viewAssembly = typeof(HtmlGeneratorService).GetTypeInfo().Assembly;
var fileProvider = new EmbeddedFileProvider(
viewAssembly,
"ApplicationServices.Widgets.Html.Templates");
services.Configure<MvcRazorRuntimeCompilationOptions>(options => {
options.FileProviders.Clear();
options.FileProviders.Add(fileProvider);
});
services.AddRazorPages().AddRazorRuntimeCompilation();

在测试项目中，我有这样的设置：

var builder = new HostBuilder()
.ConfigureWebHost(webHost =>
{
webHost.UseTestServer();
webHost.UseStartup<Startup>();
});
var host = await builder.StartAsync();
HttpClient = host.GetTestClient();

但是当我使用这个HttpClient调用我的端点时，IRazorViewEngine.GetView开始抛出奇怪的异常：

Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.CompilationFailedException: 'One or more compilation failures occurred:
rnouw0xu.21w(4,41): error CS0234: The type or namespace name 'Razor' does not exist in the namespace 'Microsoft.AspNetCore' (are you missing an assembly reference?)
rnouw0xu.21w(4,82): error CS0518: Predefined type 'System.Type' is not defined or imported
rnouw0xu.21w(4,110): error CS0518: Predefined type 'System.String' is not defined or imported
rnouw0xu.21w(4,127): error CS0518: Predefined type 'System.String' is not defined or imported
rnouw0xu.21w(8,11): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)
rnouw0xu.21w(9,11): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)
rnouw0xu.21w(10,11): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)
rnouw0xu.21w(11,11): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)
rnouw0xu.21w(13,36): error CS0234: The type or namespace name 'Rendering' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?)
rnouw0xu.21w(14,36): error CS0234: The type or namespace name 'ViewFeatures' does not exist in the namespace 'Microsoft.AspNetCore.Mvc' (are you missing an assembly reference?)
rnouw0xu.21w(29,35): error CS0234: The type or namespace name 'Razor' does not exist in the namespace 'Microsoft.AspNetCore' (are you missing an assembly reference?)
rnouw0xu.21w(29,78): error CS0518: Predefined type 'System.String' is not defined or imported
rnouw0xu.21w(29,87): error CS0518: Predefined type 'System.String' is not defined or imported

我用很多不同的方法解决了这个错误，看起来我被困在这里了。

Answer 1

看起来我在这篇文章中找到了答案：https://github.com/aspnet/Razor/issues/1212

我刚刚将此代码添加到我的test.csproj文件中：

<Target Name="CopyDepsFiles" AfterTargets="Build" Condition="'$(TargetFramework)'!=''">
<ItemGroup>
<DepsFilePaths Include="$([System.IO.Path]::ChangeExtension('%(_ResolvedProjectReferencePaths.FullPath)', '.deps.json'))" />
</ItemGroup>
<Copy SourceFiles="%(DepsFilePaths.FullPath)" DestinationFolder="$(OutputPath)" Condition="Exists('%(DepsFilePaths.FullPath)')" />
</Target>

Answer 2

由于在升级到.NET 6时建议的修复程序对我不起作用，因此仅对批准的答案进行了一点扩展，运行时仍然无法定位程序集，直到我明确地向IMvcBuilder添加了AddApplicationPart(assembly)调用。

还有一个小的简化是将选项lambda传递给AddRazordRuntimeCompilation调用，在这种情况下可以删除services.Configure<MvcRazorRuntimeCompilationOptions>。

它可能由于几个原因而失败(这是一个Windows服务项目，视图在一个单独的dll中(，但无论如何，这是我从网上收集的各种修复程序的汇编：

// this part is needed if you don't have a valid IWebHostEnvironment
// service registered, in which case you need to create your own dummy
// implementation because Razor needs IWebHostEnvironment.ApplicationName
// (it should return Assembly.GetEntryAssembly().GetName().Name, and you 
// can leave other properties null)
services.AddSingleton<IWebHostEnvironment, DummyHostingEnvironment>();
services.AddSingleton<IHostEnvironment, DummyHostingEnvironment>();
// this also needs to be registered as two separate dependencies
// if you're getting "Unable to resolve service for type
// 'System.Diagnostics.DiagnosticListener'"
// (see https://github.com/dotnet/aspnetcore/issues/14544)
var diagnosticSource = new DiagnosticListener("Microsoft.AspNetCore");
services.AddSingleton<DiagnosticSource>(diagnosticSource);
services.AddSingleton<DiagnosticListener>(diagnosticSource);
// make sure you specify correct assemblies, in case the views
// are in a separate dll
var assemblyWithTemplates = ...;
var assemblyReferencingTheRazorPackage = ...;
services
.AddRazorPages()
.AddApplicationPart(assemblyReferencingTheRazorPackage ) // <-- added this
.AddRazorRuntimeCompilation(options =>
{
// important to clear because some of them are null
options.FileProviders.Clear();
// resolve views as embedded resources
options.FileProviders.Add(new EmbeddedFileProvider(assemblyWithTemplates));
});

然后还将接受的答案中的代码添加到.csproj文件中，以便正确复制.deps文件。