Query on Support for Older .NET Versions in Aspire

[josephaw1022]

I have observed that currently, Aspire seems to support only hosting .NET 8 projects in a solution. This limitation raises a few questions and considerations, especially for teams working with older versions of .NET. Understanding the rationale behind this and the potential roadmap for supporting older .NET versions is crucial for planning and migration strategies.

Specific Questions:

1. Future Plans for Support: Is there any plan to introduce support for older .NET versions in Aspire? If so, what versions are being considered?
2. Reasoning Behind Current Limitation: What are the reasons for the current support being limited to .NET 8? Are these limitations due to technical challenges, strategic decisions, or other factors?
3. Priority and Timeline: If support for older .NET versions is planned, what is the priority level of this development? Additionally, is there a tentative timeline for when this support might be rolled out?

Context and Importance:

• Many projects and enterprises still operate on older versions of .NET. Understanding Aspire's compatibility roadmap is essential for these teams to plan their future development and potential migration strategies.
• Clarifying whether the limitation is due to technical constraints or strategic decisions can help teams understand the direction and focus of the Aspire framework.

[davidfowl]

Future Plans for Support: Is there any plan to introduce support for older .NET versions in Aspire? If so, what versions are being considered?

There are no plans. Aspire is .NET 8+ only. I'm sure people will find creative ways to run older versions of .NET though as the system is very extensible (you can run any executable/container etc).

Reasoning Behind Current Limitation: What are the reasons for the current support being limited to .NET 8? Are these limitations due to technical challenges, strategic decisions, or other factors?

It depends on which components of aspire you're talking about. There are various places where we depend on newer .NET SDK features and bug fixes (and more work will happen in this area). I also expect there to be features in component that depend on new APIs that may only be in .NET 8+ (though I'm not sure that has happened yet).

Many projects and enterprises still operate on older versions of .NET. Understanding Aspire's compatibility roadmap is essential for these teams to plan their future development and potential migration strategies.

Are you talking about unsupported versions of .NET (< 6) or .NET Framework (which we will never build in support for?)

Clarifying whether the limitation is due to technical constraints or strategic decisions can help teams understand the direction and focus of the Aspire framework.

The team is laser focused on .NET 8+, so most of the work will be in that direction from the core team. As for unblocking other scenarios, I think it'll depend on the size of the change and how disruptive it is to the core design we already have.

[josephaw1022]

I understand your question regarding whether you're referring to unsupported versions of .NET (earlier than .NET 6) or .NET Framework. My query specifically pertains to .NET Core versions, starting from 3.x onwards.

However, the core of my inquiry is about the compatibility between different versions within the .NET ecosystem, especially in the context of Aspire hosting apps. For instance, in a .NET 8 environment, it's technically feasible to import and use a .NET 6 class library within a .NET 8 web API. This compatibility aspect is what I am exploring with Aspire.

Even though Aspire may be designed to run on .NET 8, my question is whether it can also host and run applications built on .NET 6 or .NET 7.Even though Aspire may be designed to run on .NET 8, my question is whether it can also host and run applications built on .NET 6 or .NET 7.

And I do want to make a point that if this is designed for cloud native architecture and microservice design, in the context of microservices architecture where some teams may manage hundreds of microservices, the task of migrating all these services to a newer version like .NET 8 becomes a daunting and perhaps impractical endeavor if there are some breaking changes. It's important to recognize that in such environments, the feasibility and resource implications of migrating a large number of services must be a key consideration. Asking teams to move all of their .NET Core applications to .NET 8 may not be realistic or feasible.

But, if the decision to support only newer .NET versions in Aspire is definitive, I would appreciate if there could be some guidance provided on how to integrate Aspire with older .NET Core applications. This could be in the form of a sample project or detailed documentation. Specifically, it would be helpful to have examples or instructions that demonstrate the use of Aspire with older .NET Core versions, whether through executables or containerized applications.

Furthermore, looking ahead, I'm interested in understanding the forward compatibility of Aspire. Specifically, if only .NET 8 apps and upwards are to be supported, will future iterations of Aspire, perhaps running on .NET 9 or 10, still support applications built on .NET 8? In other words, if someone creates an Aspire application on .NET 9 or 10 in the future and still maintains some .NET 8 applications, will they be required to migrate these applications to the newer .NET versions to ensure compatibility with Aspire, as is currently the case with moving from .NET 3, 5, 6 or 7 to 8?"

[mitchdenny]

@josephaw1022 you raise some good question around our plans around forward compatibility. There are quite a few moving parts involved in that. What follows are some discussion points, not to be taken as a commitment ;)

The interdependency between the AppHost and constituent service projects is very lightweight. Whilst there is a reference from the service project to the app host we only use this for generating project metadata, not actually a binary reference. So, in theory a .NET 8.0 service project could be referenced by a .NET 9.0 app host.

Another integration point is how the AppHost tells the service app in the inner loop how to connect to the resources that it manages. At the moment there are two broad ways this occurs (setup via the WithReference extension). One is ConnectionString_resourcename and the other is service discovery variables (for project-to-project interactions).

Finally, we have the Aspire components themselves (code that runs inside your services). These components depend on the environment variables that are injected as connection strings combined with local service specific configuration. You could update your AppHost and not update these components, and assuming we haven't broken the integration via the environment variables it should continue to function unless the underlying client libraries were somehow incompatible with the container image being used to emulate that resource type locally.

Anytime we make changes to the AppModel/components these are the kinds of things we will need to consider.

One point I would raise is on the subject of right sizing the number of micro-services in a single AppHost. When you add resources to an app host you are kind of saying that you expect these resources to be deployed together as a unit. You might well have 100s of micro-services, but are they all closely related enough that you want to debug them all as a set, or are some of them going to be owned by different business units and you'll consume them just like any other online service (via a stable endpoint).

I realize that this doesn't give you a definitive answer, but it's a BIG question :)

[GioviQ]

I'm learning about Aspire right now, so maybe my answer is naive, but I see Aspire components that embed database servers that aren't .NET projects, so maybe you can create components to embed older .NET 6 projects.

[davidfowl]

Aspire.Hosting.* will work agnostic of your .NET version. The apphost has a target framework but it isn't relevant to what your applications use. The components are client libraries https://learn.microsoft.com/en-us/dotnet/aspire/fundamentals/components-overview?tabs=dotnet-cli that live in your application and target .NET 8+.