In a multiprocessing environment, which thread-safe collection should be used for concurrent operations?

The correct answer is B: ConcurrentBag. ConcurrentBag and other Concurrent* collections from System.Collections.Concurrent are thread-safe for multi-threaded scenarios without explicit locking.

In C#, what is the relationship between composition and inheritance in OOP design?

The correct answer is B: Inheritance should be preferred when there's an 'is-a' relationship; composition for 'has-a' relationship. Composition (HAS-A) and Inheritance (IS-A) serve different purposes. Composition is more flexible and often preferred over inheritance to avoid tight coupling.

In C#, what happens when you apply the 'static' modifier to a method inside an interface (C# 11+)?

The correct answer is B: The method provides a default implementation and can be called without instantiation. C# 11 allows static abstract members in interfaces. Static methods in interfaces provide default implementations and can be called via the interface type.

What happens when you mark a class with the 'sealed' modifier?

The correct answer is B: The class cannot be inherited from. 'sealed' keyword prevents a class from being inherited. This is useful for security and performance optimization when you want to prevent further derivation.

Which LINQ method should you use to get distinct elements from a List while maintaining performance?

The correct answer is B: list.Distinct(). Distinct() is the standard LINQ method for removing duplicates. While HashSet works, Distinct() is more idiomatic.

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C# Programming

C# and .NET for campus placement

76 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 71–76 of 76

Topics in C# Programming

All Basics & Syntax 100 OOP in C# 100 Collections 71 ASP.NET Basics 19

Q.71 Easy Basics & Syntax

Which of the following is a value type in C#?

A String

B Enum

C Interface

D Delegate

Correct Answer: B. Enum

EXPLANATION

Enum is a value type in C#. String, Interface, and Delegate are reference types.

Test

Q.72 Easy Basics & Syntax

What will be the output of the following code?
string s = "Hello";
s = s + " World";
Console.WriteLine(s);

A Hello

B Hello World

C Error

D World

Correct Answer: B. Hello World

EXPLANATION

String concatenation using '+' operator joins the two strings. s becomes 'Hello World' after the concatenation.

Test

Q.73 Easy Basics & Syntax

Which of the following is NOT a valid C# variable name?

A _myVar

B my$Var

C myVar123

D MyVar

Correct Answer: B. my$Var

EXPLANATION

Variable names in C# can contain letters, digits, and underscores. They cannot contain special characters like '$'. The variable name must start with a letter or underscore.

Test

Q.74 Easy Basics & Syntax

Which namespace is required to use Console.WriteLine() in C#?

A System.IO

B System

C System.Console

D System.Text

Correct Answer: B. System

EXPLANATION

Console class is part of the System namespace. You need to include 'using System;' at the beginning of your code to use Console.WriteLine().

Test

Q.75 Easy Basics & Syntax

Which keyword is used to create a class in C#?

A class

B Class

C CLASS

D struct

Correct Answer: A. class

EXPLANATION

C# is case-sensitive. The lowercase keyword 'class' is used to define a class. 'Class' and 'CLASS' are not valid keywords.

Test

Q.76 Easy Basics & Syntax

Which of the following is the correct syntax to declare a variable in C#?

A int x = 10;

B int x: 10;

C int x

D int x == 10;

Correct Answer: A. int x = 10;

EXPLANATION

C# uses the syntax 'type variableName = value;' to declare and initialize variables. The equals sign (=) is the assignment operator.

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