SOLID Principles in C#

What are SOLID principles? 

SOLID is an acronym for the first 5 principles of object-oriented design:

S stands for SRP “The Single Responsibility Principle”:  a class should have one, and only one, reason to change.
O stands for OCP “The Open Closed Principle”: you should be able to extend a class’s behavior, without modifying it.
L stands for LSP “The Liskov Substitution Principle”: derived classes must be substitutable for their base classes.
I stands for ISP “The Interface Segregation Principle”: make fine grained interfaces that are client specific.
D stands for DIP “The Dependency Inversion Principle”: depend on abstractions not on concrete implementations.