What will be the output of the following code? class A { public virtual void Show() { Console.WriteLine("A"); } } class B : A { public override void Show() { Console.WriteLine("B"); } } A obj = new B(); obj.Show();

The correct answer is B: B. Due to polymorphism, the overridden method in class B is called, not the virtual method in class A. Output is 'B'.

Consider the following code. What will be the output? int x = 10; int y = 20; int z = x++ + ++y; Console.WriteLine(x + " " + y + " " + z);

The correct answer is B: 11 21 31. x++ returns 10 then increments x to 11. ++y increments y to 21 then returns 21. z = 10 + 21 = 31. Final output: 11 21 31

In C# 2024-25, which LINQ method would you use to find all elements matching a condition in a List?

The correct answer is C: Both A and B work. Both FindAll() and Where() (LINQ) can filter collections. Where() returns IEnumerable and is more modern. FindAll() returns a List directly.

In C#, what is the difference between 'is' and 'as' operators?

The correct answer is A: 'is' checks type, 'as' converts type and returns null if incompatible. The 'is' operator returns a boolean indicating type compatibility. The 'as' operator performs type conversion and returns null if the conversion fails (no exception).

What is the output of the following code? class Base { public virtual void Method() { Console.WriteLine("Base"); } } class Derived : Base { public override void Method() { base.Method(); Console.WriteLine("Derived"); } } Derived d = new Derived(); d.

The correct answer is C: BaseDerived. The 'base' keyword calls the parent class method first, printing 'Base', then the derived method prints 'Derived'. Output: 'BaseDerived'.

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C# Programming
Basics & Syntax

C# and .NET for campus placement

100 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 100

Topics in C# Programming

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

Q.1 Easy Basics & Syntax

Which of the following is a correct way to declare a property with auto-implementation in C#?

A public int Age { get; set; }

B public int Age() { get; set; }

C public Age int { get; set; }

D public int get Age; set;

Correct Answer: A. public int Age { get; set; }

EXPLANATION

Auto-implemented properties in C# use the syntax: public Type PropertyName { get; set; } without explicitly defining the backing field.

Test

Q.2 Easy Basics & Syntax

Consider this code: int[] arr = new int[5]; foreach(var item in arr) { Console.Write(item + " "); } What is the output?

A Nothing (empty output)

B 0 0 0 0 0

C Throws an IndexOutOfRangeException

D Null Null Null Null Null

Correct Answer: B. 0 0 0 0 0

EXPLANATION

Arrays in C# are automatically initialized with default values. For int arrays, the default value is 0. Therefore, the output will be five zeros separated by spaces.

Test

Q.3 Medium Basics & Syntax

What is the difference between 'is' and '==' operators when comparing object references in C#?

A 'is' checks reference equality, '==' can be overloaded for value comparison

B '==' checks reference equality, 'is' checks type compatibility

C Both are identical for reference types

D 'is' only works with nullable types

Correct Answer: A. 'is' checks reference equality, '==' can be overloaded for value comparison

EXPLANATION

The 'is' operator checks reference equality by default and is used for type checking, while '==' can be overloaded by classes to provide custom equality logic.

Test

Q.4 Hard Basics & Syntax

In C# 2024, which feature allows you to use pattern matching to deconstruct objects and filter simultaneously in a single expression?

A List patterns with logical operators

B Record types with positional parameters

C Nullable reference types

D Anonymous methods

Correct Answer: A. List patterns with logical operators

EXPLANATION

C# 12 (2024) introduced advanced list patterns that allow filtering and deconstructing collections in pattern matching expressions, improving code readability and efficiency.

Test

Q.5 Medium Basics & Syntax

What will be the behavior of the following code snippet?
string str = null;
string result = str?.ToUpper() ?? "DEFAULT";
Console.WriteLine(result);

A Prints 'DEFAULT'

B Prints an empty string

C Throws NullReferenceException

D Prints 'null'

Correct Answer: A. Prints 'DEFAULT'

EXPLANATION

The null-coalescing operator (?.) with null-coalescing assignment (??) ensures that when str is null, the expression evaluates to null, and then ?? provides the default value 'DEFAULT'.

Test

Q.6 Medium Basics & Syntax

Which of the following statements about ref and out parameters in C# is correct?

A ref parameter must be initialized before passing, out parameter need not be

B out parameter must be initialized before passing, ref parameter need not be

C Both ref and out require initialization before method call

D Neither ref nor out requires initialization

Correct Answer: A. ref parameter must be initialized before passing, out parameter need not be

EXPLANATION

ref parameters must be initialized before being passed to a method, while out parameters don't require initialization beforehand. The method must assign a value to out parameters before returning.

Test

Q.7 Easy Basics & Syntax

Which collection type in C# is best suited for key-value pair storage with unique keys?

A List

B Dictionary

C HashSet

D Queue

Correct Answer: B. Dictionary

EXPLANATION

Dictionary<K, V> stores key-value pairs and ensures unique keys. List stores ordered values, HashSet stores unique values only, Queue is FIFO.

Test

Q.8 Hard Basics & Syntax

What is the output of: string s = "Hello"; Console.WriteLine(s.GetHashCode() == s.GetHashCode());

A true

B false

C NullReferenceException

D Compiler Error

Correct Answer: A. true

EXPLANATION

GetHashCode() on the same string returns the same hash code value, so comparison is true. Strings are immutable in C#.

Test

Q.9 Hard Basics & Syntax

In C# 2024, what is the latest feature for null-safety introduced in recent versions?

A Nullable reference types

B required keyword for properties

C init-only properties

D All of the above

Correct Answer: D. All of the above

EXPLANATION

C# has progressively introduced nullable reference types, required keyword (C# 11), and init-only properties (C# 9) for better null-safety and immutability.

Test

Q.10 Medium Basics & Syntax

Which of the following correctly demonstrates the ternary operator in C#?

A int x = (age >= 18) ? "adult" : "minor";

B int x = (age >= 18) ? 1 : 0;

C bool x = (age >= 18) ? true; false;

D string x = (age >= 18) ? 18 : 0;

Correct Answer: B. int x = (age >= 18) ? 1 : 0;

EXPLANATION

Option B is correct as both branches return int (1 or 0). Option A has type mismatch (string in int). Option C has wrong syntax. Option D has type mismatch.

Test

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