MCSD Programming in C# 3

Question 1

What is the purpose of the `abstract` keyword when applied to a class in C#?

Accepted Answer

Prevents instantiation and requires derived classes to implement abstract members

Answer

Makes all methods private

Answer

Allows multiple inheritance

Answer

Seals the class hierarchy

Question 2

Which C# statement is used to re-throw the current exception without losing the stack trace?

Accepted Answer

throw;

Answer

throw ex;

Answer

throw new Exception();

Answer

rethrow;

Question 3

What does the `?? ` (null coalescing) operator do in C#?

Accepted Answer

Returns the left operand if not null, otherwise returns the right operand

Answer

Checks if two values are equal

Answer

Casts a value to a nullable type

Answer

Throws an exception if null

Question 4

Which modifier makes a C# method belong to the type rather than an instance?

Accepted Answer

static

Answer

const

Answer

readonly

Answer

extern

Question 5

What is an extension method in C#?

Accepted Answer

A static method that can be called as if it were an instance method on another type

Answer

A method defined inside an interface

Answer

A method that extends the CLR

Answer

An override of a sealed method

Question 6

In C# generics, what does a `where T : class` constraint enforce?

Accepted Answer

T must be a reference type

Answer

T must be a value type

Answer

T must implement IComparable

Answer

T must have a parameterless constructor