OOPS & C# - Loops, Conditions, Exception Handling

What are the Loop types in C#?

1. While loop

2. Do While

3. For Loop

4. ForEach Loop

What is the difference between “continue” and “break” statement?

• Continue statement end the loop iteration and transfer the control to the beginning of the loop.

• Break statement end the loop iteration and exit the loop.

What are the alternative ways of writing if-else conditions?

1. Switch

2. Ternary

How to implement Exception Handling in C#?

Exception handling with Try, Catch, and Finally

Can we execute multiple Catch blocks?

NO

When to use Finally in real applications?

Finally block is mostly used to dispose the unwanted objects

Can we have only “Try” block without “Catch” block in real applications?

YES - but then we must have finally block with try block.

What is the difference between Finally and Finalize?

❖ Finally, is used in exception handling.

❖ Finalize is a method which is automatically called by the garbage collector to dispose the no longer needed objects

What is the difference between “throw ex” and “throw”?

Throw ex will change the stack trace, where as throw will preserve the whole stack trace.

Explain Generics in C#?

Make classes and methods - type independent or type safe.

EX: AreEqual<T>(T value1, T value2)

What are Collections in C# and what are their types?

Used to store, manage and manipulate data

EX: ArrayList, Dictionary, List, Hashtable

What is the difference between Array and ArrayList (atleast 2)?

1. Array is STRONGLY typed

2. Array elements are FIXED

1. ArrayList can Store any items\elements

2. ArrayList can store any amount of elements

What is the difference between Arraylist and Hashtable?

• In Arraylist we can only add Items/ Values to the list.

  • Values

• In Hashtable we can add Items/Values with the Keys.

  • Keys and Value

What is the difference between List and Dictionary Collections?

• List is a collection of items.

• It is the generic version of ArrayList

• Dictionary is a collection of key value pair.

• It is the generic version of Hashtable

What is IEnumerable in C#?

IEnumerable interface is used when we want to ITERATE among our collection classes using a FOREACH loop. 

• Interface that ITERATE collection in a FOREACH loop

What is the difference between IEnumerable and IEnumerator in C#?

• IEnumerable internally uses IEnumerator only to iterate the collection via forach loop.

• IEnumerable simplifies the use of IEnumerator.

What is the difference between IEnumerable and IQueryable in C#?

• IQueryable inherited from IEnumerable interface only

  • Anything you can do with a IEnumerable, you can also do with an IQueryable also.

• IEnumerable is used with in-memory collection.

• IQueryable is better in getting result from database.

• IQueryable is under SYSTEM.LINQ namespace. IEnuberable is under System.Collections namespace.

• IQueryable filter the result at database only and then get only filtered result, therefore less network load and better performance.