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Enabling .NET Aspire for an existing solution

I hope that you already had a change to try .NET Aspire, a comprehensive set of tools, templates, and packages designed to help developers build observable, production-ready applications. It enhances the development experience by providing dev-time orchestration, integrations with commonly used services, and robust tooling support. .The goal is to simplify the management of multi-project applications, container resources, and other dependencies, making it easier to develop interconnected apps.

To make it even better, it includes features like service discovery, connection string management, and environment variable configuration, streamlining the setup process for local development environments.

And if that couldn’t convince you yet, than maybe the Aspire Dashboard will.

Sounds great right? Reason enough to add it to your existing projects if you are not using it yet. A great tutorial exists on Microsoft Learn to help you add it to your existing projects. Unfortunately I had a little bit more trouble when trying to add it to an existing solution. In this post I want to share some of the issues I encountered when enabling .NET Aspire.

Adding .NET Aspire

Before we dive in, let me first share some details about the application involved. The solution contains 3 projects:

  • One (older) ASP.NET Core application that I upgraded to .NET 9 but was still using the old Startup.cs experience.
  • One (newer) ASP.NET Core application that was using the Minimal API approach.
  • One .NET console application that was hosting a WorkerService.

Ok, let’s get started!

  • I right click on the first project(the ASP.NET Core project using Startup.cs) and choose Add –> .NET Aspire Orchestrator Support…

  • I get a popup mentioning that 2 projects will be added to my solution. I can change the Project name prefix and location but I’m happy with the defaults so I click OK.

  • Whoops! I got an error saying that it couldn’t find a call to methods Build in the program main.

  • When I take a look at the solution however I noticed that the 2 Aspire related projects were added to the solution and that my project was added.
  • OK. Let’s try to build the project. That failed with 2 NuGet related errors. I forgot to mention that I’m using NuGet Central package management. Unfortunately the Add Aspire wizard didn’t take this into account and wrongfully added the nuget packages in the specific project files.

 

  • I manually fixed it by adding the packages myself to the Central Package Management and removing the version reference from the csproj files.

 

  • Now it’s time to add a second project. I right click on the project(the ASP.NET Core Minimal API) and choose Add –> .NET Aspire Orchestrator Support… again.

  • This time I get a message that an .NET Aspire Orchestrator project already exists and that Visual Studio will update it. Sounds fine to me! So I click OK.
  • That worked. Great!

  • Let’s do this one last time, but now for the .NET Console Application. I right click on the the project choose Add –> .NET Aspire Orchestrator Support… again.

  • I got the same message that an .NET Aspire Orchestrator project already exists. I click OK.

  • Whoops! This time he complains that he cannot find any of the Create…Builder methods.

  • However when I checked the .NET Aspire project, I noticed that the Worker project was successfully added.

The most important impact of those errors was that the default middleware (like Service Discovery, etc…) couldn’t be added automatically but the AppHost itself worked fine.

More information

.NET Aspire overview - .NET Aspire | Microsoft Learn

Add .NET Aspire to an existing .NET app - .NET Aspire | Microsoft Learn

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