I want to my azure function from v1 to v4 my current dotnet framework is 4.8 need suggestion which version should I go 4.8 or 8 or 9

@Rashmiramchandra Prabhu

Thanks for your question regarding the migration of your Azure Function from version 1 to version 4.

You're correct — when targeting .NET Framework 4.8 with Azure Functions v4 (using the in-process model), Microsoft requires changing the output type to Exe. This change can cause issues if your current project is structured as a class library, as it’s not designed for that output format. These compatibility issues are common in this scenario.

To clarify your follow-up question:

Is there an Upgrade Assistant for 4.8 with v4? No — the .NET Upgrade Assistant is not designed to assist with migrating to .NET Framework 4.8. Instead, it helps migrate projects from .NET Framework (like 4.8) to modern .NET versions such as .NET 6, 7, or 8.

For this reason, recommend migrating your Function App to .NET 8 using the isolated worker model, which:

• Allows you to keep your class library structure (no need to change to Exe)
• Offers long-term support through November 2026
• Avoids the limitations and legacy constraints of .NET Framework-based deployments

You can use the .NET Upgrade Assistant to help with this transition.

Helpful resources:

• Migrate apps from Azure Functions version 1.x to version 4.x
• Azure Functions runtime versions overview
• Guide for running C# Azure Functions in the isolated worker model

You mentioned .net 8 is long term support but my v1 is supporting till september 2026 so its like only 2 month extended support but what after that .Should I need to migrate it again to some other version?

@Rashmiramchandra Prabhu

Thank you for your question. To provide clarity on the Azure Functions support timelines:

• Your current application is running on Azure Functions v1, which is supported until September 2026.
• Azure Functions v4 is the latest supported version, and as of now, there is no published end-of-life date for v4. It remains the current version with ongoing support from Microsoft.
• If you migrate to .NET 8 (LTS) with Functions v4, the .NET 8 runtime will be supported until November 2026.

So even though .NET 8 and Functions v1 may both reach end-of-life around late 2026, once you're on v4 with isolated .NET, you'll be in a much better position to upgrade to future versions like .NET 10 LTS with minimal changes.

Please let me know if this answers your question.