Here I am listing my C# Implementations of all the 23 Design Patterns.

1. Singleton Pattern
2. Command Pattern
3. Decorator Pattern
4. Builder Pattern
5. Observer Pattern
6. Strategy Pattern
7. Template Method Pattern
8. Visitor Pattern
9. Adapter Pattern
10. Chain of Responsibility Pattern
11. Abstract Factory Pattern
12. Factory Method Pattern
13. Flyweight Pattern
14. Proxy Pattern
15. State Pattern
16. Facade Pattern
17. Iterator Pattern
18. Mediator Pattern
19. Memento Pattern
20. Prototype Pattern
21. Interpreter Pattern
22. Bridge Pattern
23. Composite Pattern

The associated source code can be found in c-sharpcorner.com.

eBook
You can find the eBook on Design Patterns below.

Video Tutorial

You can also refer to Video Tutorials on Design Patterns of .Net Mentor & my friend Shivprasad Koirala.