If-else execution flow in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested if-else statements

What is the output of this C# code?

C Sharp (C#)

int x = 10;
int y = 20;
if (x > y)
{
    Console.WriteLine("X is greater");
}
else if (x == y)
{
    Console.WriteLine("X equals Y");
}
else
{
    Console.WriteLine("Y is greater");
}

A X is greater

B X equals Y

C Y is greater

D No output

💡 Hint

Compare the values of x and y carefully.

Since x (10) is less than y (20), the else block runs, printing "Y is greater".

❓ Predict Output

intermediate

If-else with boolean conditions

What will this program print?

C Sharp (C#)

bool isRaining = false;
bool haveUmbrella = true;
if (isRaining && haveUmbrella)
{
    Console.WriteLine("Go outside");
}
else
{
    Console.WriteLine("Stay inside");
}

A Stay inside

B Compilation error

C Go outside

D No output

💡 Hint

Both conditions must be true for the first block to run.

isRaining is false, but haveUmbrella is true. The condition isRaining && haveUmbrella is false, so the else block runs, printing "Stay inside".

🔧 Debug

advanced

Identify the error in if-else syntax

Which option contains a syntax error in the if-else structure?

C Sharp (C#)

int number = 5;
if (number > 0)
    Console.WriteLine("Positive");
else
    Console.WriteLine("Non-positive");

A

if (number > 0)
    Console.WriteLine("Positive")
else
    Console.WriteLine("Non-positive");

B

if (number > 0) {
    Console.WriteLine("Positive");
} else {
    Console.WriteLine("Non-positive");
}

C

if (number > 0)
    Console.WriteLine("Positive");
else
    Console.WriteLine("Non-positive");

D

if number > 0 {
    Console.WriteLine("Positive");
} else {
    Console.WriteLine("Non-positive");
}

💡 Hint

Check the syntax for the if statement in C#.

Option D misses parentheses around the condition, which is required in C#. This causes a syntax error.

❓ Predict Output

advanced

Output of if-else with multiple conditions

What does this program print?

C Sharp (C#)

int score = 85;
if (score >= 90)
{
    Console.WriteLine("Grade A");
}
else if (score >= 80)
{
    Console.WriteLine("Grade B");
}
else if (score >= 70)
{
    Console.WriteLine("Grade C");
}
else
{
    Console.WriteLine("Grade F");
}

A Grade F

B Grade B

C Grade C

D Grade A

💡 Hint

Check which condition matches the score first.

The score 85 is not >= 90, so first if fails. The second condition (>= 80) is true, so it prints "Grade B" and skips the rest.

🧠 Conceptual

expert

Understanding if-else execution flow with variable changes

Consider this code snippet. What is the final value of result after execution?

C Sharp (C#)

int x = 5;
int result = 0;
if (x > 3)
{
    result = 10;
    if (x < 10)
    {
        result += 5;
    }
    else
    {
        result += 20;
    }
}
else
{
    result = -10;
}

A 15

B 10

C 20

D -10

💡 Hint

Trace the nested if-else carefully and update result step by step.

Since x is 5, the first if is true, so result becomes 10. Then the nested if checks if x is less than 10, which is true, so 5 is added. Final result is 15.

Practice

1. What does the else block do in an if-else statement in C#?

easy

A. Runs before the if block

B. Runs when the if condition is true

C. Runs only if there is no if block

D. Runs when the if condition is false

Solution

1. Step 1: Understand the if-else structure

   The if block runs when its condition is true.

2. Step 2: Role of the else block

   The else block runs only when the if condition is false.

3. Final Answer:

   Runs when the if condition is false -> Option D

4. Quick Check:

   else runs if if is false [OK]

Hint: Else runs only if if-condition is false [OK]

Common Mistakes:

• Thinking else runs when if is true
• Confusing else with else if
• Believing else runs before if

2. Which of the following is the correct syntax for an if-else statement in C#?

easy

A. if (condition) { } else { }

B. if condition { } else { }

C. if (condition) then { } else { }

D. if condition then { } else { }

Solution

1. Step 1: Check C# syntax rules

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

2. Step 2: Identify correct syntax

   Only if (condition) { } else { } uses parentheses and curly braces correctly.

3. Final Answer:

   if (condition) { } else { } -> Option A

4. Quick Check:

   Parentheses and braces required in C# if-else [OK]

Hint: Use parentheses around condition and braces for blocks [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using 'then' keyword incorrectly
• Missing curly braces

3. What is the output of this C# code?

int x = 5;
if (x > 10) {
    Console.WriteLine("Greater");
} else {
    Console.WriteLine("Smaller or equal");
}

medium

A. No output

B. Greater

C. Smaller or equal

D. Compilation error

Solution

1. Step 1: Evaluate the condition x > 10

   Since x is 5, 5 > 10 is false.

2. Step 2: Determine which block runs

   The else block runs because the if condition is false, printing "Smaller or equal".

3. Final Answer:

   Smaller or equal -> Option C

4. Quick Check:

   5 > 10 is false, so else runs [OK]

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

Common Mistakes:

• Assuming if block runs when condition is false
• Confusing output strings
• Thinking code has syntax errors

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

int num = 7;
if num > 5 {
    Console.WriteLine("Big");
} else {
    Console.WriteLine("Small");
}

medium

A. Missing parentheses around condition

B. Missing semicolon after if statement

C. Missing curly braces around else block

D. Incorrect variable type

Solution

1. Step 1: Check if statement syntax

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

2. Step 2: Identify the error

   The code lacks parentheses around num > 5, causing a syntax error.

3. Final Answer:

   Missing parentheses around condition -> Option A

4. Quick Check:

   If condition must be in parentheses [OK]

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

Common Mistakes:

• Forgetting parentheses around condition
• Adding semicolon after if line
• Misplacing curly braces

5. You want to print "Positive", "Negative", or "Zero" based on an integer variable num. Which if-else structure correctly implements this?

hard

A. if (num > 0) { Console.WriteLine("Positive"); } else if (num <= 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); }

B. if (num > 0) { Console.WriteLine("Positive"); } else { if (num < 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); } }

C. if (num >= 0) { Console.WriteLine("Positive"); } else if (num <= 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); }

D. if (num > 0) { Console.WriteLine("Positive"); } else if (num > 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); }

Solution

1. Step 1: Understand the conditions needed

   We need to check if num is positive, negative, or zero.

2. Step 2: Analyze each option's logic

   if (num > 0) { Console.WriteLine("Positive"); } else { if (num < 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); } } correctly nests the else-if logic to handle all three cases without overlap or error.

3. Final Answer:

   if (num > 0) { Console.WriteLine("Positive"); } else { if (num < 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); } } -> Option B

4. Quick Check:

   Nested else-if covers all cases correctly [OK]

Hint: Use nested else if or else if for multiple conditions [OK]

Common Mistakes:

• Using overlapping conditions
• Missing zero case
• Repeating same condition twice