What does the Count property of a collection return in C#?

The correct answer is B: The current number of elements in the collection. Count returns the number of elements currently stored. Capacity is different and refers to allocated space.

Consider: Dictionary dict = new(); dict.Add("a", 1); dict.Add("a", 2); What happens?

The correct answer is B: ArgumentException is thrown. Dictionary enforces unique keys. Attempting to add a duplicate key throws ArgumentException. Use dict["a"] = 2 to update.

What will be the output of: int x = 10; int y = 20; int z = x > y ? x : y; Console.WriteLine(z);

The correct answer is B: 20. The ternary operator checks if x > y. Since 10 is not greater than 20, it returns y which is 20.

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

The correct answer is B: 0 0 0 0 0. 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.

Which statement about method overloading in C# is correct?

The correct answer is B: Methods can have the same name if they differ in parameter types or count. Method overloading requires different parameter types, count, or order. Return type alone is not enough. C# fully supports overloading.

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C# Programming
Basics & Syntax

C# and .NET for campus placement

15 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–15 of 15

Topics in C# Programming

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

Q.11 Hard Basics & Syntax

What is the difference between 'struct' and 'class' in C# regarding memory allocation?

A Both are allocated on the heap

B Both are allocated on the stack

C struct is allocated on the stack, class on the heap

D struct is allocated on the heap, class on the stack

Correct Answer: C. struct is allocated on the stack, class on the heap

EXPLANATION

Value types (struct) are allocated on the stack, while reference types (class) are allocated on the heap.

Test

Q.12 Hard Basics & Syntax

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

A Throws exception

B Creates new array with 5 elements, preserving first 3 values

C Returns null

D Changes original array size

Correct Answer: B. Creates new array with 5 elements, preserving first 3 values

EXPLANATION

Array.Resize() creates a new array of specified size and copies elements from the original array using the ref parameter.

Test

Q.13 Hard Basics & Syntax

Which of the following is NOT a valid C# data type?

A sbyte

B uint

C float32

D decimal

Correct Answer: C. float32

EXPLANATION

C# has float (4 bytes) and double (8 bytes), but not float32. sbyte, uint, and decimal are valid types.

Test

Q.14 Hard Basics & Syntax

Which of the following statements about structs and classes in C# is TRUE?

A Structs are reference types, classes are value types

B Structs are value types, classes are reference types

C Both are reference types

D Both are value types

Correct Answer: B. Structs are value types, classes are reference types

EXPLANATION

In C#, structs are value types (stored on stack) while classes are reference types (stored on heap). This is a fundamental difference between the two.

Test

Q.15 Hard Basics & Syntax

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

A 10 20 30

B 11 21 31

C 11 21 30

D 10 21 31

Correct Answer: B. 11 21 31

EXPLANATION

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

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C# Programming
Basics & Syntax