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

An abstract class cannot be instantiated directly and may contain abstract members that subclasses must implement.

Question 2

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

Accepted Answer

throw;

Answer

Using `throw;` alone re-throws the current exception preserving the original stack trace.

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

The `??` operator returns the left-hand operand if it is not null; otherwise, it returns the right-hand operand.

Question 4

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

Accepted Answer

static

Answer

The `static` modifier means the method belongs to the class itself, not to any object instance.

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

Extension methods are static methods in a static class that can be invoked using instance method syntax on the extended type.

MCSD Exam Practice Test