What is the space complexity of a HashSet with n elements storing unique values?

The correct answer is A: O(n). HashSet requires O(n) space to store n unique elements. Hash tables require linear space proportional to the number of stored elements.

In a hospital management system, Doctor and Nurse classes need to perform a common Logout() operation but have different Login() procedures. What is the best OOP approach?

The correct answer is A: Create a base class with virtual Logout() and abstract Login(). A base class with virtual Logout() allows common implementation, while abstract Login() forces derived classes to provide their own implementation. This combines code reuse with flexibility.

Which collection allows duplicate keys in C#?

The correct answer is C: List. List allows duplicates as it stores elements sequentially. Dictionary and Hashtable enforce unique keys; attempting to add a duplicate key throws an exception.

Which keyword is used to prevent a class from being inherited in C#?

The correct answer is B: sealed. 'sealed' keyword prevents a class from being inherited in C#. 'final' is Java syntax. 'abstract' requires a class to be inherited. 'static' makes members class-level, not related to inheritance.

What happens when a derived class constructor does not explicitly call the base class constructor in C#?

The correct answer is B: Parameterless base constructor is called automatically. C# automatically calls the parameterless constructor of the base class if no explicit base() call is made, ensuring base class initialization.

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C# Programming

C# and .NET for campus placement

154 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 151–154 of 154

Topics in C# Programming

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

Q.151 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.152 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.153 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.154 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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