Why conditional flow control is needed in C Sharp (C#) - See It in Action

Why conditional flow control is needed

📖 Scenario: Imagine you are building a simple program that decides if a person can enter a club based on their age. The club only allows people who are 18 years or older.

🎯 Goal: You will create a program that uses conditional flow control to check a person's age and print whether they can enter the club or not.

📋 What You'll Learn

Create an integer variable called age with the value 20

Create an integer variable called minimumAge with the value 18

Use an if statement to check if age is greater than or equal to minimumAge

Print "Access granted" if the condition is true

Print "Access denied" if the condition is false

💡 Why This Matters

🌍 Real World

Conditional flow control is used in many real-world programs to make decisions, like checking user permissions, validating input, or controlling game logic.

💼 Career

Understanding conditional statements is essential for any programming job because it allows you to write programs that respond differently to different situations.

1

Create the age variable

Create an integer variable called age and set it to 20.

C Sharp (C#)

// Your code here

Hint

Use int to declare the variable and assign the value 20.

2

Create the minimum age variable

Create an integer variable called minimumAge and set it to 18.

C Sharp (C#)

int age = 20;
// Your code here

Hint

Use int to declare the variable and assign the value 18.

3

Add the conditional check

Use an if statement to check if age is greater than or equal to minimumAge. Inside the if, write a comment // Access granted. Add an else block with a comment // Access denied.

C Sharp (C#)

int age = 20;
int minimumAge = 18;
// Your code here

Hint

Use if (age >= minimumAge) to check the condition and else for the other case.

4

Print the result

Replace the comments inside the if and else blocks with Console.WriteLine("Access granted"); and Console.WriteLine("Access denied"); respectively to print the result.

C Sharp (C#)

int age = 20;
int minimumAge = 18;
if (age >= minimumAge)
{
    // Your code here
}
else
{
    // Your code here
}

Hint

Use Console.WriteLine to print the messages inside the blocks.

Practice

1. Why do we use conditional flow control like if and else in C# programs?

easy

A. To repeat the same code many times

B. To make decisions and run different code based on conditions

C. To store data in variables

D. To create new classes and objects

Solution

1. Step 1: Understand the purpose of conditional flow

   Conditional flow lets the program choose which code to run depending on a condition.

2. Step 2: Compare with other options

   Repeating code is done by loops, storing data is done by variables, and creating objects is done by classes, not conditionals.

3. Final Answer:

   To make decisions and run different code based on conditions -> Option B

4. Quick Check:

   Conditional flow = decision making [OK]

Hint: If code runs differently by condition, use if/else [OK]

Common Mistakes:

• Confusing conditionals with loops
• Thinking variables control flow
• Mixing object creation with flow control

2. Which of the following is the correct syntax for a simple if statement in C#?

easy

A. if (x > 0) Console.WriteLine("Positive") end

B. if x > 0 then Console.WriteLine("Positive")

C. if x > 0: Console.WriteLine("Positive")

D. if (x > 0) { Console.WriteLine("Positive"); }

Solution

1. Step 1: Recall C# if statement syntax

   C# requires parentheses around the condition and braces for the code block.

2. Step 2: Check each option

   if (x > 0) { Console.WriteLine("Positive"); } uses correct parentheses and braces. The other options use syntax from other languages or invalid endings.

3. Final Answer:

   if (x > 0) { Console.WriteLine("Positive"); } -> Option D

4. Quick Check:

   Correct C# if syntax = if (x > 0) { Console.WriteLine("Positive"); } [OK]

Hint: Remember: if(condition) { code } in C# [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using Python or VB syntax by mistake
• Missing braces for code block

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

int number = 10;
if (number > 5)
{
    Console.WriteLine("Greater than 5");
}
else
{
    Console.WriteLine("5 or less");
}

medium

A. Greater than 5

B. 5 or less

C. No output

D. Syntax error

Solution

1. Step 1: Evaluate the condition

   The variable number is 10, which is greater than 5, so the condition is true.

2. Step 2: Determine which block runs

   Since the condition is true, the code inside the if block runs, printing "Greater than 5".

3. Final Answer:

   Greater than 5 -> Option A

4. Quick Check:

   10 > 5 is true, so prints "Greater than 5" [OK]

Hint: Check if condition is true or false to pick output [OK]

Common Mistakes:

• Confusing which block runs on true condition
• Assuming else runs even if if is true
• Thinking no output if condition true

4. Find the error in this C# code snippet:

int age = 20;
if age >= 18
{
    Console.WriteLine("Adult");
}

medium

A. Variable age is not declared

B. Missing semicolon after Console.WriteLine

C. Missing parentheses around the condition in if statement

D. Braces {} are not allowed in if statements

Solution

1. Step 1: Check if statement syntax

   C# requires parentheses around the condition in an if statement.

2. Step 2: Verify other parts

   Console.WriteLine has semicolon, braces are allowed, and age is declared correctly.

3. Final Answer:

   Missing parentheses around the condition in if statement -> Option C

4. Quick Check:

   if(condition) needs parentheses [OK]

Hint: Always put condition inside parentheses in if [OK]

Common Mistakes:

• Forgetting parentheses in if condition
• Thinking braces are optional and cause errors
• Assuming variable is undeclared when it is declared

5. You want to write a program that prints "Good morning" if the hour is less than 12, "Good afternoon" if the hour is between 12 and 17 (inclusive), and "Good evening" otherwise. Which code correctly uses conditional flow control?

hard

A. if (hour < 12) { Console.WriteLine("Good morning"); } else if (hour <= 17) { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); }

B. if (hour < 12) { Console.WriteLine("Good morning"); } if (hour <= 17) { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); }

C. if (hour < 12) { Console.WriteLine("Good morning"); } else { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); }

D. if (hour < 12) Console.WriteLine("Good morning"); else if (hour < 17) Console.WriteLine("Good afternoon"); else Console.WriteLine("Good evening");

Solution

1. Step 1: Understand the conditions needed

   We need three cases: less than 12, between 12 and 17 inclusive, and greater than 17.

2. Step 2: Check each option's logic

   if (hour < 12) { Console.WriteLine("Good morning"); } else if (hour <= 17) { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); } correctly uses if, else if, and else with correct conditions including <= 17. if (hour < 12) { Console.WriteLine("Good morning"); } if (hour <= 17) { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); } uses two separate ifs causing multiple prints. if (hour < 12) { Console.WriteLine("Good morning"); } else { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); } has two else blocks which is invalid. if (hour < 12) Console.WriteLine("Good morning"); else if (hour < 17) Console.WriteLine("Good afternoon"); else Console.WriteLine("Good evening"); uses < 17 instead of <= 17, missing hour 17 case.

3. Final Answer:

   if (hour < 12) { Console.WriteLine("Good morning"); } else if (hour <= 17) { Console.WriteLine("Good afternoon"); } else { Console.WriteLine("Good evening"); } -> Option A

4. Quick Check:

   Use if, else if, else with correct ranges [OK]

Hint: Use else if for multiple exclusive conditions [OK]

Common Mistakes:

• Using multiple ifs causing multiple outputs
• Writing multiple else blocks
• Incorrect condition ranges missing edge values