Runar Ovesen Hjerpbakk

Programmer. Software Architect. Technical Manager.

ASP.Net Core

Creating an ASP.Net Core app with a React frontend and Docker hosting

I started a new project this week, a SPA written in React with an ASP.Net Core 2.1.1 backend hosted in a Docker container. This is the tale of how I got all those pieces working together.

The running code from this article can be seen on GitHub.

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Error RZ3007 - Targeted tag name cannot be null or whitespace.

The first release candidate of ASP.NET Core 2.1 is out with a lot of performance improvements and new features.

One of the features is Razor compilation on build, enabling catching more errors at design time and improved startup time. This however broke one of my apps.

After updating the app to 2.1, navigating to a Razor view met me with the following error:

Microsoft.AspNetCore.Mvc.Razor.Compilation.CompilationFailedException: One or more compilation failures occurred:
(0,0): Error RZ3007: Targeted tag name cannot be null or whitespace.
   at Microsoft.AspNetCore.Mvc.Razor.Internal.RazorViewCompiler.CompileAndEmit(String relativePath)
   at Microsoft.AspNetCore.Mvc.Razor.Internal.RazorViewCompiler.OnCacheMiss(String normalizedPath)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Razor.Internal.DefaultRazorPageFactoryProvider.CreateFactory(String relativePath)
   at Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine.CreateCacheResult(HashSet`1 expirationTokens, String relativePath, Boolean isMainPage)
   at Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine.OnCacheMiss(ViewLocationExpanderContext expanderContext, ViewLocationCacheKey cacheKey)
   at Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine.LocatePageFromViewLocations(ActionContext actionContext, String pageName, Boolean isMainPage)
   at Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine.FindView(ActionContext context, String viewName, Boolean isMainPage)
   at Microsoft.AspNetCore.Mvc.ViewEngines.CompositeViewEngine.FindView(ActionContext context, String viewName, Boolean isMainPage)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor.FindView(ActionContext actionContext, ViewResult viewResult)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor.ExecuteAsync(ActionContext context, ViewResult result)
   at Microsoft.AspNetCore.Mvc.ViewResult.ExecuteResultAsync(ActionContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultAsync(IActionResult result)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResultFilterAsync[TFilter,TFilterAsync]()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResultExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultFilters()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
   at Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at MediaServer.Startup.<>c__DisplayClass5_0.<<Configure>b__0>d.MoveNext() in /Users/sankra/projects/MediaServer/MediaServer/Startup.cs:line 104
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.ResponseCaching.ResponseCachingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware:Error: An unhandled exception has occurred while executing the request.

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.dockerignore is your friend

While working on a particular project built with a multi-stage Dockerfile I got this error:

Step 13/19 : RUN dotnet test "./DashboardServerTests/DashboardServerTests.csproj" -c Release --no-restore
 ---> Running in ac850e55464c
Build started, please wait...
/usr/share/dotnet/sdk/2.0.3/Sdks/Microsoft.NET.Sdk/build/Microsoft.PackageDependencyResolution.targets(323,5): error : Assets file '/Users/sankra/projects/DashboardServer/Grafana/obj/project.assets.json' not found. Run a NuGet package restore to generate this file. [/source/Grafana/Grafana.csproj]

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Running ASP.Net Core web app in a Docker container using a multi-stage Dockerfile

Lately. I’ve written multiple web applications with ASP.Net Core. Together with C# newfound cross-platformness, this stack is a joy to work with.

I user Docker to run the applications, some in Azure, some on on-premise Linux boxes. This has thought me a couple of things. Firstly, the app should be built from within a container using a multi-stage Dockerfile.

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An assembly specified in the application dependencies manifest was not found

This happened a while ago, but might be relevant again in the future.

I created a website using ASP.Net Core and ran it through a Docker Container.

docker run kitchen-responsible

Worked perfectly for a long time, but after updating a nuget package it started to fail with:

  An assembly specified in the application dependencies manifest (KitchenResponsibleService.deps.json) was not found:
	package: 'Microsoft.AspNetCore.Antiforgery', version: '2.0.1'
	path: 'lib/netstandard2.0/Microsoft.AspNetCore.Antiforgery.dll'
  This assembly was expected to be in the local runtime store as the application was published using the following target manifest files:

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