This article details the modernization of legacy WCF services from .NET Framework 4.x to CoreWCF on .NET 6, enabling Linux deployment and reducing Microsoft licensing costs.

• Ported WCF services to CoreWCF and .NET 6 to eliminate IIS dependency and enable Linux hosting
• Identified service with least complexity and fewest dependencies for initial upgrade
• Manually created dependency trees and upgraded nested dependencies in correct order
• Implemented multi-framework builds supporting both .NET 4.x and .NET 6 simultaneously
• Migrated configuration from web.config to startup code due to CoreWCF limitations
• Converted WCF behaviors from configuration files to programmatic setup in Startup.cs
• Refactored APM asynchronous patterns to Task-based async/await for CoreWCF compatibility
• Replaced IIS with Kestrel web server and migrated HTTP handlers/modules to middleware
• Used compiler directives to maintain framework-specific code for backward compatibility
• Containerized services for deployment on Amazon EKS to improve scalability

The modernization approach enables cost reduction through Linux deployment while maintaining backward compatibility with 80+ existing WCF service consumers.