Which of the following is NOT a pillar of OOP in C#?

The correct answer is D: Compilation. The four pillars of OOP are Inheritance, Polymorphism, Encapsulation, and Abstraction. Compilation is a language feature, not an OOP principle.

Which IEnumerable method should be used to filter elements based on a condition and maintain type safety?

The correct answer is A: Where. Where is a LINQ method that filters elements based on a predicate condition while maintaining type safety in the collection.

What is the primary purpose of encapsulation in OOP?

The correct answer is B: To hide internal implementation details and control access to data. Encapsulation bundles data and methods together, hiding internal implementation and controlling access through public interfaces, improving maintainability and security.

In ASP.NET Core, what is the purpose of the appsettings.json file?

The correct answer is A: To store application configuration settings. appsettings.json stores application configuration like connection strings, logging levels, and custom settings.

Which access modifier allows access from derived classes only?

The correct answer is C: protected. protected members are accessible from the same class and derived classes, but not from outside the class hierarchy.

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C# Programming
Basics & Syntax

C# and .NET for campus placement

56 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 51–56 of 56

Topics in C# Programming

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

Q.51 Medium Basics & Syntax

Which of the following correctly declares a nullable integer in C#?

A int? x = null;

B int x = null;

C nullable int x = null;

D int* x = null;

Correct Answer: A. int? x = null;

EXPLANATION

In C#, 'int?' is used to declare a nullable integer. A regular 'int' cannot be assigned null. int* is a pointer (unsafe code), not a nullable type.

Test

Q.52 Medium Basics & Syntax

Which of the following will correctly convert a string to an integer in C#?

A int x = (int)"123";

B int x = int.Parse("123");

C int x = Convert.ToInt32("abc");

D int x = "123" as int;

Correct Answer: B. int x = int.Parse("123");

EXPLANATION

int.Parse() converts a string to an integer. Direct casting doesn't work for strings. Convert.ToInt32() would throw an exception if the string is not a valid number. The 'as' operator doesn't work for strings to primitives.

Test

Q.53 Medium Basics & Syntax

What is the difference between '==' and 'Equals()' when comparing strings in C#?

A '==' compares references, Equals() compares values

B '==' compares values, Equals() compares references

C Both do the same thing

D '==' is for primitive types, Equals() is for objects

Correct Answer: A. '==' compares references, Equals() compares values

EXPLANATION

For strings, '==' compares references (memory addresses) while Equals() compares the actual string values. However, C# has optimized string comparison, so both often behave similarly for string literals.

Test

Q.54 Medium Basics & Syntax

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

A const int MAX = 100;

B final int MAX = 100;

C static int MAX = 100;

D readonly int MAX = 100;

Correct Answer: A. const int MAX = 100;

EXPLANATION

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.

Test

Q.55 Medium Basics & Syntax

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

A string

B int

C object

D array

Correct Answer: B. int

EXPLANATION

int is a value type (primitive type). string, object, and arrays are reference types in C#.

Test

Q.56 Medium Basics & Syntax

What will be the output of the following code snippet?
int x = 5;
int y = ++x;
Console.WriteLine(x + " " + y);

A 5 5

B 6 6

C 5 6

D 6 5

Correct Answer: B. 6 6

EXPLANATION

++x is pre-increment. It increments x first (x becomes 6), then assigns the value to y. So both x and y are 6.

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