The five design principles the SOLID acronym stands for are, using Andras' brief description:Single Responsibility Principle states that every object should only have one reason to change, i.e. every object should perform one thing only. Open-Closed Principle states that classes should be open for extension and closed for modification. Liskov Substitution Principle states that you should be able to use a derived class in place of a parent class and it must behave in the same manner. Interface Segregation Principle states that clients should not be forced to depend on interfaces they do not use. Dependency Inversion Principle helps to decouple your code by ensuring that you depend on abstractions rather than concrete implementations.

http://www.infoq.com/news/2013/08/solid-principles-revisited

S-Single responsibility principle. (A class should have only a single responsibility.)O-Open/closed principle (software entities … should be open for extension, but closed for modification.)L-Liskov substitution principle (objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program.)I-Interface segregation principle (many client-specific interfaces are better than one general-purpose interface)D-Dependency inversion principle (one should Depend upon Abstractions. Do not depend upon concretions.Dependency injection is one method of following this principle.)

SOLID are five basic principles whichhelp to create good software architecture. SOLID is an acronym where:-S stands for SRP (Single responsibility principle O stands for OCP (Open closed principle) L stands for LSP (Liskov substitution principle) I stands for ISP ( Interface segregation principle) D stands for DIP ( Dependency inversion principle)

I have recently found a very nice article on this topic at the below link: http://www.codeproject.com/Articles/703634/SOLID-architecture-principles-using-simple-Csharp

http://www.codeproject.com/Articles/60845/The-S-O-L-I-D-Object-Oriented-Programming-OOP-Prin

http://www.infoq.com/news/2013/08/solid-principles-revisited/