Dependency Validation Diagrams do not work in ASP.NET Core / .NET Core


Dependency validation helps to keep the code architecture clean and rules enforced. The video below gives a quick introduction to the dependency validation in Visual Studio.

Recently a friend, asked about enforcing constraints in a project architecture, I explained this to him. But I haven’t used it any of my previous projects (we’re good developers who do not spoil the code :P) , so thought of giving it a try. As shown in the video things should be straight forward but I ended up my validations never kicked in.

With some investigation, I found that when we add the DV project to the solution it adds the following package to all the projects.


If your project is made out from a .net core / core project template then it fails to install the above NuGet package and obviously the validation does not work.

How to fix this ?

I created a ASP.NET Core project based on .NET Framework (same applies to .NET Core as well). Added some class libraries and draw a following dependency validation layered diagram.

Layered Diagram

Red one is the web project ( core) and others are simple class libraries. The structure is not complex. Just to check the validation, I referenced the DataContext in the web project as below.

public void ConfigureServices(IServiceCollection services)
// This is right
services.AddSingleton<IProductService, ProductService>();
// this is wrong and DV should fail
services.AddSingleton<IMyDbContext, MyDbContext>();

But the validation never fired.

In order to do get this work.

  • Install the following NuGet in the ASP.NET Core / .NET Core template based projects in the solution. Other projects have it installed automatically when we add the DV project.
Install-Package Microsoft.DependencyValidation.Analyzers -Version 0.9.0
  • Open the ASP.NET Core template project file. Add the following. line numbers 15-18 should be manually added to include the DV diagram in the core web project.

<Project Sdk="Microsoft.NET.Sdk.Web">
<Folder Include="wwwroot\" />
<PackageReference Include="Microsoft.DependencyValidation.Analyzers" Version="0.9.0" />
<AdditionalFiles Include="..\DependencyValidation\DependencyValidation.layerdiagram">
<ProjectReference Include="..\LayeredProject.DataContext\LayeredProject.DataContext.csproj" />
<ProjectReference Include="..\LayeredProject.Services\LayeredProject.Services.csproj" />

After this all set with one small problem. Now, when we build the project, the validation kicks and the build will fail.

But the error response from Visual Studio is not consistence. It will always fail the build – that’s 100% expected behavior and it is right. But sometimes the error only appears in the Output window and not in the Error List. Also, sometimes the red squiggly does not appear.

This happens because the ASP.NET Core / .NET Core project templates do not support the DV, we did a workaround to make it work and it has some links broken to display the error message in the Error List, I hope soon Microsoft will add support to the DV in ASP.NET Core and .NET Core based project templates.

You can check  / reproduce this, using the following two branches. The ‘normal’ branch has problem and the ‘solved’ branch is patch applied.

Used tooling

  • VS 2017 Enterprise (15.7.4)
  • ASP.NET Core 2.1
  • .NET Framework 4.7.1



Detailing ASP.NET Core in Azure App Service

ASP.NET core is the next generation development standard for the .NET world – may be that’s how I like to express it. Every ASP.NET Core application is a DNX (.NET Execution Environment) application.

When you create an ASP.NET Core application in Visual Studio (VS) 2015, it creates the project targeted at both the .NET Framework and .NET Core. You can see this under the frameworks section of the project.json file. Also the ASP.NET Core team recommends to leave this settings as it is. (Refer : letting your application targets both the frameworks.

But in order to understand how things are deployed in the Azure App Service, I compiled an ASP.NET Core application and published it to an Azure Web App. Then I browsed the app with Kudu services and the Process Explorer looked like this, which shows ASP.NET Core app is running on DNX.


Under the Debug Console of the Kudu services in the following path site\approot\runtimes we can see the shipped .NET Core runtime, a feature which makes ASP.NET Core applications self-contained.


All these information are hidden from the developers and let them focus on the application development. So though the Visual Studio publishing model of the ASP.NET Core application is same as ASP.NET application publish model, based on the defined configurations Azure App Service hosts your web application under different runtimes.