Request for Microsoft guidance: Migration strategy from VB.NET/ASP.NET MVC/System.Web to .NET 10

Dear Microsoft Support Team,

We are currently evaluating a modernization strategy for an existing enterprise system, GMTP/F-GDC, and would like to request Microsoft's official technical guidance before deciding on our migration approach.

1. Current system

Our system is a long-running enterprise application with the following technology stack:

• VB.NET

ASP.NET MVC on System.Web

.NET Framework

TERASOLUNA Framework (legacy .NET version)

Microsoft Enterprise Library

SQL Server

Windows Server

The system consists of:

Web application: approximately 69 GSK screens

Web Services: legacy ASMX services

Batch/Report: approximately 27 BSK and 49 FSK applications

Business Common library

Common Framework library

WinForms/Console tools

SSIS

Excel/Access VBA macros

Some third-party/legacy components include:

Microsoft.Practices.EnterpriseLibrary.*

Microsoft.Web.Mvc.dll

MvcContrib

NVelocity

log4net

ICSharpCode.SharpZipLib

ExcelCreator

Legacy TERASOLUNA Framework components

Our target platform under consideration is:

.NET 10

ASP.NET Core

C#

SQL Server 2019 or later

Modern Windows Server / potentially Linux or container environments

2. Main question: VB.NET support on .NET 10

The most important issue for us is the future of VB.NET.

We understand that VB.NET can be used for class libraries, console applications, batch applications and WinForms applications on modern .NET.

However, our understanding is that VB.NET is not supported for developing ASP.NET Core applications.

Could Microsoft please confirm officially:

Is VB.NET supported for ASP.NET Core applications on .NET 10?

Is VB.NET supported for ASP.NET Core MVC applications on .NET 10?

Is VB.NET supported for ASP.NET Core Web API applications on .NET 10?

Does Microsoft have any roadmap or plan to support VB.NET for ASP.NET Core Web/API development in future .NET releases?

If ASP.NET Core does not support VB.NET, is the recommended migration path to rewrite the Web/API layer in C# while keeping reusable business logic in VB.NET class libraries where technically possible?

This point is critical because our existing Web and ASMX Web Service applications are written in VB.NET.

3. .NET Framework 4.8 and long-term support

If we decide to temporarily keep the existing Web application on .NET Framework 4.8, we would like Microsoft's recommendation regarding its long-term support model.

Specifically:

What is Microsoft's current support policy for .NET Framework 4.8?

How does .NET Framework 4.8 support depend on the underlying Windows Server operating system?

If we upgrade the production environment to Windows Server 2022 or Windows Server 2025, how long can we reasonably continue running an ASP.NET MVC/System.Web application on .NET Framework 4.8?

Is there any Microsoft recommendation for enterprises that need to keep ASP.NET MVC/System.Web applications running for several more years while gradually migrating to ASP.NET Core?

Are there any important security or compatibility risks that Microsoft recommends specifically reviewing when moving an existing ASP.NET MVC application to .NET Framework 4.8?

4. Migration strategy

We are considering four possible strategies.

Option A — Full Freeze

Keep the entire system on:

VB.NET

ASP.NET MVC/System.Web

.NET Framework 4.8

Windows Server 2022/2025

No immediate migration to .NET 10.

Option B — Hybrid

Keep:

Web/WebService → VB.NET + .NET Framework 4.8

Modernize:

Batch

Business Common

Tools

to:

VB.NET

.NET 10

Option C — Full Modernization

Rewrite:

Web → C# + ASP.NET Core + .NET 10

Web Service → C# + ASP.NET Core Web API + .NET 10

Batch → .NET 10

Business Common → .NET 10

Tools → .NET 10

The goal would be to eventually have the entire system on modern .NET.

Option D — Incremental Modernization / Strangler Pattern

Keep the existing VB.NET/ASP.NET MVC application running while gradually developing individual GSK screens in:

C#

ASP.NET Core

.NET 10

The old and new applications would temporarily run in parallel, with routing/reverse proxy technology directing users to either the legacy or modern application.

Eventually, all GSK screens would be migrated and the legacy ASP.NET MVC/System.Web application would be retired.

5. Microsoft's recommended strategy

Based on Microsoft's experience with large enterprise applications, which of the above approaches would Microsoft recommend for a system of this type?

In particular, we would appreciate guidance on:

Is incremental modernization (Option D) a recommended approach for a large ASP.NET MVC/System.Web application?

Is it technically reasonable to run ASP.NET MVC/.NET Framework 4.8 and ASP.NET Core/.NET 10 applications side-by-side for several years?

What Microsoft technologies would you recommend for routing traffic between the legacy and modern applications?

IIS URL Rewrite

  YARP

  
     Other Microsoft-supported technologies

     
     What is the recommended approach for authentication and authorization when users need to move between the legacy application and the new ASP.NET Core application?

     
     What is the recommended approach for sharing session/state between the two applications, if required?

     
     Are there any Microsoft-recommended patterns for gradually replacing individual ASP.NET MVC screens with ASP.NET Core applications?
```## 6. Business logic and shared libraries

Our Business Common and Framework libraries contain significant business logic written in VB.NET.

We would like to avoid rewriting business logic unnecessarily.

Could Microsoft advise whether the following architecture is reasonable?

Legacy:


```sql
ASP.NET MVC / VB.NET / .NET Framework 4.8
         |
         +---- Business Common

Modern:

ASP.NET Core / C# / .NET 10
         |
         +---- Business Common

If the shared Business Common is migrated to modern .NET, can it remain implemented in VB.NET while being consumed by a C# ASP.NET Core application?

If yes, what project target framework would Microsoft recommend for such shared libraries?

Would you recommend:

.NET 10 class libraries

.NET Standard 2.0

Multi-targeting

Another approach

We are particularly interested in avoiding unnecessary dependency on .NET Standard 2.0 if it is not required.

7. Legacy technologies

We also have dependencies on several legacy technologies.

Could Microsoft provide guidance on the recommended modern replacements or migration approach for:

System.Web

ASP.NET MVC 5

ASMX Web Services

Microsoft Enterprise Library

Microsoft.Web.Mvc

MvcContrib

NVelocity

Legacy TERASOLUNA Framework components

Web.config-based configuration

log4net

For ASMX services specifically:

Would Microsoft recommend migrating directly from:

ASMX / VB.NET

to:

ASP.NET Core Web API / C# / .NET 10

or is there an intermediate migration approach that Microsoft recommends?

8. Third-party components

One important third-party dependency is ExcelCreator.

Before migrating our Batch/Report applications to .NET 10, we need to determine whether the vendor library is officially compatible with modern .NET.

Does Microsoft have any recommended compatibility assessment process or tooling for identifying whether existing .NET Framework dependencies can be migrated to .NET 10?

9. Our expected migration direction

Our current technical assumption is:

Legacy Web
VB.NET + ASP.NET MVC + System.Web
          |
          | temporarily remain on .NET Framework 4.8
          |
          v

Common/Business/Batch
gradually migrate to .NET 10
          |
          v

Web Service
migrate to C# + ASP.NET Core Web API
          |
          v

Web screens
gradually migrate from VB.NET MVC
to C# + ASP.NET Core + .NET 10
          |
          v

Eventually retire .NET Framework/System.Web

Before adopting this strategy, we would like Microsoft to confirm whether this is a technically sound and supported modernization direction.

10. Requested response

We would appreciate Microsoft's official recommendations regarding:

VB.NET support and future roadmap for ASP.NET Core.

Long-term support considerations for .NET Framework 4.8.

Recommended migration strategy for large ASP.NET MVC/System.Web applications.

Whether an incremental/Strangler migration is recommended.

Recommended Microsoft technologies for running legacy ASP.NET MVC and ASP.NET Core applications side-by-side.

Recommended approach for authentication/session/state during the transition.

Recommended strategy for sharing or migrating VB.NET business logic to .NET 10.

Recommended migration path from ASMX to ASP.NET Core Web API.

Recommended approach for replacing Enterprise Library and other legacy Microsoft libraries.

Any official Microsoft documentation, reference architecture, migration guides, or tools that you recommend for this type of enterprise modernization.

This information will be used as a technical basis for selecting the migration strategy and preparing the detailed modernization plan for GMTP/F-GDC.

Thank you for your support.

Best regards, GMTP/F-GDC Development TeamDear Microsoft Support Team,

We are currently evaluating a modernization strategy for an existing enterprise system, GMTP/F-GDC, and would like to request Microsoft's official technical guidance before deciding on our migration approach.