Liskov Substitution Principle: SubType (Child Class)Must be Substitutable For Base Type(Base Class).

LSP comes into use when you use inheritance/Abstraction.

Rules:

1.Child Class Should not remove Base Class Behaviour.

2.Child Class Should not violate base class invariants.

In short,the Calling code should not know whether it is calling the base class or derived class.

#49:SOLID-Open Closed Principle

#48 SOLID-Single Responsibility

#47: throwing Exception

you can throw exception in two ways.

1.throw. This will throw the caught exception.The throwed exception must be caught again.It will not reset the stack trace.

2.throw e or throw new CustomException : It behaves exactly same but it will reset the stack trace.

Experimentation of Throw vs Throw ex(throw new CustomException):

DivByZero Method:

private static void DivByZero()
 {
 int j = 0;
 var result = 9/j; //Line No :45 in my program is the  Cause of Exception
 }

1.Throw:It does not reset the stack trace,instead preserves it and throws the exception

private static void thrwonigException(){
 try
 {
 DivByZero();
 }catch (DivideByZeroException e)
 {
 /*It will not reset stack trace,instead throws the caught exception */.
 throw ;
 }
}

It still maintains the line which causes the exception,

2.Throw e : Returns the line no 34 as cause of exception but not 45,the stack trace is reset after this line

private static void thrwonigException(){
try
 {
 DivByZero();
 }
 catch (DivideByZeroException e)
 {
 /*It will reset the stack trace and tells that this line is the cause of exception.
 * It will not who caused the exception.
 * */
 throw e; //or throw new DivideByZeroException();
 }
}

#46 Exception Handling Mechnaism

C# Provides try,catch and finally mechanism to handle Exception.

try: Business logic code block,potentially might cause exception

catch: Block where all your exceptions are caught.

Finally:Block which always executes after try/catch irrespective of exceptions.( P.S: Stackoverflow will make the finally block not to execute)

Rules:

1.There must be finally block after try,If you do not have a catch block.

2.There can be two or more catch blocks.

3.Ordering of Catching Exception Matters.

4.Exception is the base of all other ExceptionClasses.

 try
 {
 /*your code here*/
 }
 catch(Exception exception)
 {
 /* Exeption caught if something goes wrong*/
 }
 finally
 {
 /*Guaranteed to run even if exception occurs.This block will always run*/
 Console.WriteLine();
 /*
 * Clean UP Code.
 */
 }