Unit 2: C# Programming Fundamentals - Practice Quiz

1 Which C# data type is commonly used to store a whole number?

2 Which symbol is used to assign a value to a variable in C#?

3 Which method displays text on the console and moves to the next line?

4 Which method is used to read a complete line of input from the console?

5 Which statement prints Hello, World! in a C# console program?

6 Which statement is used to execute code when a condition is true?

7 Which keyword provides an alternative block when an if condition is false?

8 Which loop is commonly used when the number of repetitions is known?

9 Which loop checks its condition before executing its body?

10 Which jump statement immediately exits a loop?

11 Which statement skips the remaining statements in the current loop iteration?

12 What is the index of the first element in a C# array?

13 Which property returns the number of elements in a C# array?

14 Which method converts all letters in a string to uppercase?

15 Which property returns the number of characters in a string?

16 Which collection stores elements as key-value pairs?

17 What is a method in C#?

18 What is an object in C#?

19 When is a constructor usually called?

20 Which access modifier allows a member to be accessed from any code that can see the class?

21 What is the value of result after this code executes?

int count = 5;
double result = count / 2;

22 Which statement correctly reads an integer entered by the user and stores it in age?

23 Which statement is required to display Hello, World! in a standard C# console program?

24 What is printed by the following code?

int marks = 72;
if (marks >= 80)
    Console.Write("A");
else if (marks >= 60)
    Console.Write("B");
else
    Console.Write("C");

25 How many times is Console.Write(i); executed?

for (int i = 1; i <= 10; i += 2)
{
    Console.Write(i);
}

26 What is printed by this code?

for (int i = 1; i <= 5; i++)
{
    if (i == 3)
        continue;
    Console.Write(i);
}

27 What is the value of numbers[2] after this code executes?

int[] numbers = { 4, 8, 12, 16 };
numbers[2] = numbers[0] + numbers[1];

28 What is the value of text after this code executes?

string text = "  CSharp  ";
text = text.Trim().ToUpper();

29 Which collection is most appropriate when items must be accessed by a unique string key?

30 What is printed by the following code?

static void Update(int x)
{
    x = 20;
}

int value = 10;
Update(value);
Console.Write(value);

31 Which code correctly creates an object from the following class?

class Student
{
    public string Name;
}

32 What is the purpose of the constructor in this class?

class Product
{
    public string Code;

    public Product(string code)
    {
        Code = code;
    }
}

33 A field should be accessible only inside its own class. Which access modifier provides this restriction?

34 Which design best demonstrates encapsulation for a bank account balance?

35 Which situation best illustrates abstraction?

36 Given class Dog : Animal, which statement is correct?

37 What concept is demonstrated when a derived class provides its own implementation of a base class method declared with virtual?

38 Which block executes whether or not an exception occurs?

39 Which statement correctly reads all text from a file named data.txt?

40 A program produces the wrong result but runs without crashing. Which debugging action is most useful for locating the cause?

41 What does the following C# code print?

byte b = 250;
try
{
checked
{
b += 10;
}
Console.Write($"V{b}");
}
catch (OverflowException)
{
Console.Write($"E{b}");
}

42 Standard input contains exactly one empty line followed by end-of-file. What does this code print?

string? a = Console.ReadLine();
string? b = Console.ReadLine();
Console.Write($"{a?.Length ?? -1},{b?.Length ?? -1}");

43 In a C# 12 console project, what is written to standard output by this program?

Console.Write("T");

class Program
{
public static void Main() => Console.Write("M");
}

44 What value is printed?

int x = 0;
bool A() { x += 1; return false; }
bool B() { x *= 10; return true; }

if (A() && B() || B())
x += 3;

Console.Write(x);

45 What value does the following loop print?

int sum = 0;
for (int i = 0; i < 4; i++)
{
switch (i)
{
case 1: continue;
case 2: break;
}
sum += i;
}
Console.Write(sum);

46 What does this program print?

static int F()
{
int x = 1;
try
{
return x;
}
finally
{
x = 2;
Console.Write(x);
}
}

Console.Write(F());

47 What does the following code print?

object[] values = new string[2];
values[0] = "ok";

try
{
values[1] = new object();
Console.Write("A");
}
catch (ArrayTypeMismatchException)
{
Console.Write("B");
}

Console.Write(values[0]);

48 What does this code print?

string s = "A\U0001F600B";
string t = s.Substring(1, 2);
Console.Write($"{s.Length}:{t.Length}:{char.IsSurrogatePair(t, 0)}");

49 What does the following code print?

var values = new List<int> { 1, 2, 3 };
try
{
foreach (int value in values)
{
if (value == 2)
values.Remove(value);
Console.Write(value);
}
}
catch (InvalidOperationException)
{
Console.Write("E");
}

50 What values are printed?

static void Update(int a, ref int b, out int c)
{
a++;
b += a;
c = a + b;
}

int x = 2;
Update(x, ref x, out int y);
Console.Write($"{x},{y}");

51 What does this object-initializer code print?

class Counter
{
private int x;
public int X
{
get => x;
set { x = value; Y = x + 1; }
}
public int Y { get; set; }
}

var c = new Counter { Y = 10, X = 3 };
Console.Write($"{c.X},{c.Y}");

52 What is the output when new C() executes?

class C
{
public C() : this(1) { Console.Write("A"); }
private C(int n) : this("x") { Console.Write("B"); }
private C(string s) { Console.Write("C"); }
}

53 Assembly A defines the following class:

public class Base
{
private protected int P;
protected internal int Q;
}

Assembly B, which has no friend-assembly access to A, defines class Derived : Base. Inside an instance method of Derived, variables Base b and Derived d are available. Which statement compiles?

54 A class stores data in private readonly List<int> _items. A view obtained by a caller must reflect later internal additions, but callers must not be able to mutate the list through that view. Which implementation best satisfies both requirements?

55 Consider this C# 12 code:

interface I
{
void M() => Console.Write("I");
}

abstract class A : I { }
class B : A { }

Which statement correctly describes the two expressions ((I)new B()).M() and new B().M()?

56 What does this program print?

class Base
{
public string Name() => "B";
}

class Derived : Base
{
public new string Name() => "D";
}

Derived d = new Derived();
Base b = d;
Console.Write(d.Name() + b.Name());

57 What does the following code print?

class Base
{
public virtual string F(object value) => "BO";
}

class Derived : Base
{
public override string F(object value) => "DO";
public string F(string value) => "DS";
}

Base x = new Derived();
Console.Write(x.F("text"));

58 What value is printed?

int x = 0;
try
{
throw new InvalidOperationException();
}
catch (Exception) when (++x == 0)
{
x += 100;
}
catch (InvalidOperationException)
{
x += 10;
}
finally
{
x *= 2;
}
Console.Write(x);

59 Assume path is writable and initially unused. What content is printed?

File.WriteAllText(path, "abcdef");
using (var stream = new FileStream(path, FileMode.Open, FileAccess.Write))
{
stream.WriteByte((byte)'X');
}
Console.Write(File.ReadAllText(path));

60 A debugger must retain the original exception throw site after the exception is logged in a catch block. Which replacement for RETHROW satisfies that requirement?

catch (Exception ex)
{
Log(ex);
RETHROW
}