Which LINQ method combines multiple sequences into a single result with cartesian product?

The correct answer is B: SelectMany(). SelectMany() (also called flatMap in other languages) flattens nested sequences and creates a cartesian product of collections.

What is the correct way to declare a constant variable in C#?

The correct answer is A: const int MAX = 100;. The 'const' keyword is used to declare constants in C#. 'final' is Java syntax. While 'readonly' can be used, 'const' is the proper keyword for compile-time constants.

What will be the result of: string text = null; Console.WriteLine(text ?? "Default");

The correct answer is B: Default. The null-coalescing operator (??) returns the right operand if the left is null. Since text is null, it prints 'Default'.

Consider: int[] arr = {1, 2, 3}; What happens when you try to resize it using Array.Resize(ref arr, 5)?

The correct answer is B: Creates new array with 5 elements, preserving first 3 values. Array.Resize() creates a new array of specified size and copies elements from the original array using the ref parameter.

What is the output of: bool result = (5 > 3) && (3 < 2); Console.WriteLine(result);

The correct answer is B: false. The && operator requires both conditions to be true. (5 > 3) is true, but (3 < 2) is false. Since one condition is false, the entire expression evaluates to false.

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C# Programming
Basics & Syntax

C# and .NET for campus placement

29 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–29 of 29

Topics in C# Programming

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

Q.21 Easy Basics & Syntax

What will be the output of: Console.WriteLine(10 / 3);

A 3.33

B 3

C 3.333333

D Compilation error

Correct Answer: B. 3

EXPLANATION

Integer division in C# truncates the decimal part. 10 / 3 = 3 (not 3.33) because both operands are integers.

Test

Q.22 Easy Basics & Syntax

Which of the following correctly declares a variable that can hold null?

A int x = null;

B int? x = null;

C string x;

D object x = null;

Correct Answer: B. int? x = null;

EXPLANATION

Only nullable types (using ?) can hold null values for value types. int? is a nullable integer that can hold null.

Test

Q.23 Easy Basics & Syntax

What is the default access modifier for a class member in C#?

A public

B private

C protected

D internal

Correct Answer: B. private

EXPLANATION

The default access modifier for class members in C# is private, meaning they are accessible only within the same class.

Test

Q.24 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.25 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.26 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.27 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.28 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.29 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.

Test

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