For loop execution model in C Sharp (C#) - Mini Project: Build & Apply

For loop execution model

📖 Scenario: Imagine you are organizing a small event and want to count how many guests will attend. You have a list of guest names, and you want to print each name one by one using a loop.

🎯 Goal: You will create a list of guest names, set up a counter, use a for loop to go through each guest, and print their names one by one.

📋 What You'll Learn

Create a list of guest names with exact values

Create an integer variable to count guests

Use a for loop with a counter variable to iterate over the list

Print each guest name inside the loop

Print the total number of guests after the loop

💡 Why This Matters

🌍 Real World

Counting and listing items is common in many programs, like showing guest lists, product inventories, or task lists.

💼 Career

Understanding how for loops work with lists is a basic skill needed for software development, data processing, and automation tasks.

1

Create the guest list

Create a List<string> called guests with these exact names: "Alice", "Bob", "Charlie", "Diana", "Ethan".

C Sharp (C#)

// Create the guest list with exact names
// Your code here

Hint

Use List<string> and initialize it with the exact names inside curly braces.

2

Create a guest counter

Create an integer variable called guestCount and set it to guests.Count to store the number of guests.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List guests = new List { "Alice", "Bob", "Charlie", "Diana", "Ethan" };
        // Create guestCount variable
        // Your code here
    }
}

Hint

Use int guestCount = guests.Count; to get the number of guests.

3

Use a for loop to print each guest

Use a for loop with an integer variable i starting at 0, running while i < guestCount, and increasing i by 1 each time. Inside the loop, print the guest name at index i from guests.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List guests = new List { "Alice", "Bob", "Charlie", "Diana", "Ethan" };
        int guestCount = guests.Count;
        // Use a for loop to print each guest
        // Your code here
    }
}

Hint

Use for (int i = 0; i < guestCount; i++) and inside the loop print guests[i].

4

Print the total number of guests

After the for loop, print the total number of guests using Console.WriteLine with the exact text: Total guests: followed by the value of guestCount.

C Sharp (C#)

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List guests = new List { "Alice", "Bob", "Charlie", "Diana", "Ethan" };
        int guestCount = guests.Count;
        for (int i = 0; i < guestCount; i++)
        {
            Console.WriteLine(guests[i]);
        }
        // Print total guests
        // Your code here
    }
}

Hint

Use Console.WriteLine("Total guests: " + guestCount); after the loop.

Practice

1. What are the three main parts of a for loop in C#?

easy

A. Declaration, execution, and termination

B. Initialization, condition check, and increment/decrement

C. Start, middle, and end

D. Input, process, and output

Solution

1. Step 1: Understand the structure of a for loop

   A for loop has three parts inside parentheses: initialization, condition, and increment/decrement.

2. Step 2: Match parts to options

   Initialization sets the start value, condition checks if the loop continues, and increment/decrement changes the variable each time.

3. Final Answer:

   Initialization, condition check, and increment/decrement -> Option B

4. Quick Check:

   for loop parts = initialization, condition, increment [OK]

Hint: Remember: start, check, change in for loop [OK]

Common Mistakes:

• Confusing for loop parts with general program steps
• Thinking for loop has only two parts
• Mixing up condition and increment roles

2. Which of the following is the correct syntax for a basic for loop in C# that counts from 0 to 4?

easy

A. for (int i = 0; i < 5; i++) { }

B. for int i = 0; i < 5; i++ { }

C. for (int i = 0; i < 4; i++) { }

D. for (i = 0; i < 5; i++) { }

Solution

1. Step 1: Check syntax correctness

   In C#, the for loop syntax requires parentheses around initialization, condition, and increment, and braces for the loop body.

2. Step 2: Validate each option

   for (int i = 0; i < 4; i++) { } only counts 0 to 3 (missing 4); for int i = 0; i < 5; i++ { } misses parentheses; for (int i = 0; i < 5; i++) { } is correct syntax counting 0 to 4; for (i = 0; i < 5; i++) { } misses type declaration for i.

3. Final Answer:

   for (int i = 0; i < 5; i++) { } -> Option A

4. Quick Check:

   Correct for loop syntax uses parentheses and semicolons [OK]

Hint: Use parentheses and semicolons in for loop header [OK]

Common Mistakes:

• Omitting parentheses around for loop parts
• Missing type declaration for loop variable
• Using wrong comparison operators

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

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

medium

A. 1 2 3

B. 0 1 2 3

C. 1 2 3 4

D. 3 2 1

Solution

1. Step 1: Analyze loop range

   The loop starts at i=1 and runs while i is less than or equal to 3, so it runs for i=1, 2, 3.

2. Step 2: Determine output per iteration

   Each iteration prints the current i followed by a space, so output is "1 ", "2 ", "3 ".

3. Final Answer:

   1 2 3 -> Option A

4. Quick Check:

   Loop prints 1 to 3 with spaces [OK]

Hint: Check loop start and end values carefully [OK]

Common Mistakes:

• Assuming loop starts at 0 instead of 1
• Including an extra number beyond the condition
• Printing in reverse order

4. Identify the error in this C# for loop:

for (int i = 0; i < 5; i++)
    Console.WriteLine(i);
    Console.WriteLine("Done");

medium

A. Infinite loop due to wrong condition

B. Syntax error: semicolon missing after for statement

C. Loop variable i is not declared

D. Missing braces causes only first line to loop

Solution

1. Step 1: Check loop body structure

   Without braces, only the first statement after for is inside the loop; the second statement runs once after the loop.

2. Step 2: Understand effect on output

   "Done" prints once after loop finishes, which might be unexpected if intended inside loop.

3. Final Answer:

   Missing braces causes only first line to loop -> Option D

4. Quick Check:

   Use braces to include multiple statements in loop [OK]

Hint: Use braces {} for multiple statements in loops [OK]

Common Mistakes:

• Assuming all lines are inside loop without braces
• Thinking semicolon is needed after for header
• Confusing variable declaration errors

5. You want to print all even numbers from 2 to 10 using a for loop in C#. Which loop header correctly achieves this?

hard

A. for (int i = 0; i < 10; i += 2)

B. for (int i = 1; i <= 10; i++) if (i % 2 == 0)

C. for (int i = 2; i <= 10; i += 2)

D. for (int i = 2; i < 10; i++) if (i % 2 == 0)

Solution

1. Step 1: Understand the goal

   We want to print even numbers from 2 to 10 inclusive, so loop variable should start at 2 and go up to 10.

2. Step 2: Check each option

   for (int i = 2; i <= 10; i += 2) increments by 2 starting at 2, so it prints 2,4,6,8,10. for (int i = 1; i <= 10; i++) if (i % 2 == 0) has a condition inside loop but header increments by 1; it works but is less efficient. for (int i = 0; i < 10; i += 2) starts at 0 and stops before 10, missing 10. for (int i = 2; i < 10; i++) if (i % 2 == 0) increments by 1 and stops before 10, missing 10.

3. Final Answer:

   for (int i = 2; i <= 10; i += 2) -> Option C

4. Quick Check:

   Increment by 2 from 2 to 10 for even numbers [OK]

Hint: Increment by 2 starting at 2 for even numbers [OK]

Common Mistakes:

• Using i++ and filtering inside loop instead of incrementing by 2
• Starting loop at 0 or 1 instead of 2
• Stopping loop before reaching 10