.NET Framework to .NET Modernization Program Playbook

The .NET Framework is Windows-only and maintenance-mode; modern .NET is cross-platform, faster, and container-friendly. This program moves a portfolio of Framework applications to current .NET, replacing legacy stacks like ASP.NET MVC/WebForms, WCF, and EF6 with their modern equivalents, then containerizing for cloud deployment.

Phase-by-Phase

Portfolio Assessment. Scan each application for Framework-only dependencies, Windows-specific APIs, and unsupported packages. Classify apps by type (web, service, desktop-adjacent) and rehost/replatform/refactor disposition. Sequence waves with the 7 Rs strategy so effort matches business value.

Library and Data Access Migration. Convert projects to the SDK-style format, migrate EF6 to EF Core, and replace APIs that have no cross-platform equivalent. Capture a regression suite before behavior changes. Shared libraries migrate first so downstream apps inherit a clean base.

Web and Service Migration. Port ASP.NET MVC and WebForms to ASP.NET Core, and replace WCF with gRPC or REST following API-first design. Externalize configuration from web.config into a modern config store per twelve-factor principles.

Containerize and Deploy. Build Linux container images, deploy to Kubernetes or an equivalent orchestrator, and validate production parity under load. Blue-green deployment and SLO gates protect the cutover.

Team and Roles

An architect owns target patterns and the WCF replacement strategy. Backend engineers do the porting; QA owns regression and parity testing. DevOps builds images and pipelines, and SRE validates production behavior and leads cutover.

Risks and Mitigations

Windows-only dependencies (registry, GDI, COM interop) can block cross-platform moves; the assessment flags them so teams plan replacements or keep specific apps on Windows containers. API incompatibility is caught by the regression suite. Performance regressions are validated away before cutover. Coordinate shared-library waves to avoid duplicate work.

Success Criteria

Success means higher deployment frequency, lower infrastructure cost from Linux hosting, improved MTTR, and verified cross-platform parity. Framework runtimes should be retired by program end.

Tooling

Use modern .NET SDK projects, Docker for Linux images, Kubernetes for orchestration, and GitHub Actions for CI/CD. PostgreSQL or the existing relational store backs the EF Core data layer.