Single-dimensional array declaration in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an integer array named numbers with 5 elements.

C Sharp (C#)

int[] numbers = new int[[1]];

Drag options to blanks, or click blank then click option'

A3

B5

C7

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong number for the array size.

Forgetting to specify the size in the brackets.

The code declares an integer array with 5 elements using new int[5].

2fill in blank

medium

Complete the code to declare a string array named fruits with 4 elements.

C Sharp (C#)

string[] fruits = new string[[1]];

Drag options to blanks, or click blank then click option'

A4

B2

C6

D8

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a wrong size number.

Not matching the array size with the intended number of elements.

The array fruits is declared with 4 elements using new string[4].

3fill in blank

hard

Fix the error in the code to declare a double array named values with 3 elements.

C Sharp (C#)

double[] values = new double[[1]];

Drag options to blanks, or click blank then click option'

A3

B0

C5

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero or negative numbers for array size.

Using a size different from the intended number of elements.

The array values must have 3 elements, so the size should be 3.

4fill in blank

hard

Fill both blanks to declare a char array named letters with 6 elements and initialize it with default values.

C Sharp (C#)

char[] letters = new char[[1]] [2];

Drag options to blanks, or click blank then click option'

A6

B{}

C[]

D()

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong brackets for initialization.

Not specifying the correct array size.

The array letters is declared with 6 elements and initialized with empty braces {} to set default values.

5fill in blank

hard

Complete the code to declare a boolean array named flags with 4 elements and initialize all elements to false.

C Sharp (C#)

bool[] flags = new bool[[1]] { };

Drag options to blanks, or click blank then click option'

A4

B{

Cfalse, false, false, false

D}

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to close the braces.

Not matching the number of values with the array size.

The array flags is declared with 4 elements and initialized with all elements set to false using braces and values.

Practice

1. Which of the following correctly declares a single-dimensional array of integers in C#?

easy

A. int[] numbers = new int[5];

B. int numbers = new int[5];

C. int[] numbers = int[5];

D. int numbers[] = new int();

Solution

1. Step 1: Understand array declaration syntax

   In C#, a single-dimensional array is declared by specifying the type followed by square brackets and then initializing with 'new' and size.

2. Step 2: Check each option

   int[] numbers = new int[5]; correctly uses 'int[] numbers = new int[5];'. Others have syntax errors or wrong types.

3. Final Answer:

   int[] numbers = new int[5]; -> Option A

4. Quick Check:

   Correct array declaration = int[] numbers = new int[5]; [OK]

Hint: Remember: type[] name = new type[size]; for arrays [OK]

Common Mistakes:

• Forgetting square brackets after type
• Not using 'new' keyword
• Declaring array without size or initializer

2. Which of the following is the correct syntax to declare and initialize a single-dimensional string array with 3 elements in C#?

easy

A. string[] names = new string[2] {"Anna", "Bob", "Cara"};

B. string names[] = {"Anna", "Bob", "Cara"};

C. string[] names = new string {"Anna", "Bob", "Cara"};

D. string[] names = new string[] {"Anna", "Bob", "Cara"};

Solution

1. Step 1: Understand array initialization syntax

   In C#, you can initialize an array with values using 'new type[] { values }' or just '{ values }' if declaration and initialization are combined.

2. Step 2: Check each option

   string[] names = new string[] {"Anna", "Bob", "Cara"}; is fully correct. string[] names = new string[2] {"Anna", "Bob", "Cara"}; incorrectly specifies size 2 with 3 initializers (compile error). string names[] = {"Anna", "Bob", "Cara"}; uses invalid syntax. string[] names = new string {"Anna", "Bob", "Cara"}; invalid syntax (missing array dimensions).

3. Final Answer:

   string[] names = new string[] {"Anna", "Bob", "Cara"}; -> Option D

4. Quick Check:

   Explicit array init with new string[] = string[] names = new string[] {"Anna", "Bob", "Cara"}; [OK]

Hint: Use 'new type[] { ... }' for explicit array initialization [OK]

Common Mistakes:

• Specifying size with initializer list
• Using C-style array syntax
• Omitting 'new' keyword incorrectly

3. What will be the output of the following C# code?

int[] arr = new int[3] {10, 20, 30};
Console.WriteLine(arr[1]);

medium

A. 20

B. 10

C. 30

D. Runtime error

Solution

1. Step 1: Understand array indexing

   Arrays in C# are zero-based, so arr[0] = 10, arr[1] = 20, arr[2] = 30.

2. Step 2: Identify the printed element

   The code prints arr[1], which is 20.

3. Final Answer:

   20 -> Option A

4. Quick Check:

   arr[1] = 20 [OK]

Hint: Remember arrays start at index 0 in C# [OK]

Common Mistakes:

• Confusing index 1 with index 0
• Expecting output to be 10 or 30
• Thinking array indexes start at 1

4. Identify the error in the following C# code snippet:

int[] values;
values = new int[3];
values[3] = 100;

medium

A. Array size is not specified

B. Index out of range error

C. Missing array initialization

D. Syntax error in declaration

Solution

1. Step 1: Check array size and indexing

   The array 'values' is declared with size 3, so valid indexes are 0, 1, and 2.

2. Step 2: Analyze the assignment

   Assigning to values[3] is invalid and causes an IndexOutOfRangeException at runtime.

3. Final Answer:

   Index out of range error -> Option B

4. Quick Check:

   Accessing index 3 in size 3 array causes error [OK]

Hint: Array indexes go from 0 to size-1 only [OK]

Common Mistakes:

• Using index equal to array size
• Forgetting zero-based indexing
• Assuming array auto-expands

5. You want to declare a single-dimensional array of 4 doubles and initialize it with values 1.1, 2.2, 3.3, and 4.4. Which code snippet correctly does this and allows you to change the third element later?

hard

A. double[] data = new double[3] {1.1, 2.2, 3.3, 4.4}; data[2] = 5.5;

B. double[] data = new double[3]; data[2] = 5.5;

C. double[] data = new double[4] {1.1, 2.2, 3.3, 4.4}; data[2] = 5.5;

D. double data[] = new double[] {1.1, 2.2, 3.3, 4.4}; data[3] = 5.5;

Solution

1. Step 1: Check array declaration and initialization

   double[] data = new double[4] {1.1, 2.2, 3.3, 4.4}; data[2] = 5.5; declares an array of size 4 with initial values and allows modification of elements.

2. Step 2: Verify element modification

   double[] data = new double[3] {1.1, 2.2, 3.3, 4.4}; data[2] = 5.5; incorrectly specifies size 3 with 4 initializers (compile error). double data[] = new double[] {1.1, 2.2, 3.3, 4.4}; data[3] = 5.5; uses invalid syntax but index 3 is valid for size 4 array. double[] data = new double[3]; data[2] = 5.5; declares size 3, not 4, missing initialization.

3. Final Answer:

   double[] data = new double[4] {1.1, 2.2, 3.3, 4.4}; data[2] = 5.5; -> Option C

4. Quick Check:

   Explicit size and initializer with modifiable element = double[] data = new double[4] {1.1, 2.2, 3.3, 4.4}; data[2] = 5.5; [OK]

Hint: Use 'new type[size] {values}' to declare and initialize arrays [OK]

Common Mistakes:

• Mismatching array size and initializer count
• Using wrong index for element change
• Omitting 'new' keyword in some contexts