CQRS and Event Sourcing (edit)

https://www.codeguru.com/whitepapers/using-command-query-responsibility-segregation-cqrs.html

SOLID

https://www.codeguru.com/csharp/.net/net_general/netframeworkclasses/solid-design-principles-with-implementation-in-c.html

SQL Server Transaction

https://www.codeguru.com/csharp/.net/net_data/handling-transactions-in-.net-using-transactionscope.html

Excel & Charts

https://www.codeguru.com/csharp/csharp/cs_misc/com/creating-excel-charts-in-c.html

DB Unit Test

https://www.codeguru.com/csharp/.net/net_data/create-sql-server-database-unit-tests-using-visual-studio.html

WinForms TabControl

https://www.codeguru.com/csharp/.net/net_asp/controls/adding-close-buttons-to-tab-pages-with-.net.html