If statement execution flow in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of an if statement in C#?

An if statement checks a condition and runs a block of code only if that condition is true.

beginner

What happens when the condition in an if statement is false?

The code inside the if block is skipped, and the program continues with the next statement after the if block.

beginner

Explain the flow of an if-else statement.

If the if condition is true, its block runs. If false, the else block runs instead.

intermediate

What is the role of else if in C#?

else if lets you check multiple conditions one after another. The first true condition runs its block, and the rest are skipped.

intermediate

How does the program decide which block to execute in an if-else if-else chain?

It checks each condition from top to bottom. The first condition that is true runs its block, and the rest are ignored. If none are true, the else block runs.

What happens if the if condition is false and there is no else block?

A The program skips the <code>if</code> block and continues after it.

B The program runs an error.

C The program stops running.

D The program runs the <code>if</code> block anyway.

If the if condition is false and no else block exists, the program skips the if block and continues with the next statements.

In an if-else if-else chain, how many blocks can run?

A All blocks run.

B Only the <code>else</code> block runs.

C Only the first true condition's block runs.

D None run.

Only the first block with a true condition runs. The rest are skipped.

Which keyword allows checking multiple conditions in sequence?

A else

B else if

C switch

D for

else if lets you check multiple conditions one after another.

What is the correct syntax to start an if statement in C#?

A if (condition) { }

B if condition { }

C if: condition { }

D if [condition] { }

The correct syntax is if (condition) { } with parentheses around the condition.

What does the program do after finishing an if block?

A It repeats the <code>if</code> block.

B It stops running.

C It jumps to the start of the program.

D It continues with the next statement after the <code>if</code> block.

After an if block, the program continues with the next statement in order.

Describe how an if-else if-else statement controls the flow of a program.

Think about how the program chooses which code to run based on conditions.

Explain what happens when an if condition is false and there is no else block.

Consider what the program does when the condition is not met and no alternative is given.

Practice

1. What does an if statement do in C#?

easy

A. It defines a new variable.

B. It repeats code multiple times.

C. It chooses which code to run based on a condition.

D. It stops the program immediately.

Solution

1. Step 1: Understand the purpose of if

   An if statement checks a condition to decide which code runs next.

2. Step 2: Compare options

   Only It chooses which code to run based on a condition. describes choosing code based on a condition, which matches the if statement's role.

3. Final Answer:

   It chooses which code to run based on a condition. -> Option C

4. Quick Check:

   if chooses code path = C [OK]

Hint: If checks true/false to pick code path quickly [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if defines variables
• Believing if stops program

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

easy

A. if (x > 5) Console.WriteLine("Yes") end

B. if x > 5 then Console.WriteLine("Yes")

C. if x > 5: Console.WriteLine("Yes")

D. if (x > 5) { Console.WriteLine("Yes"); }

Solution

1. Step 1: Review C# if syntax

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

2. Step 2: Check each option

   if (x > 5) { Console.WriteLine("Yes"); } uses parentheses and braces correctly; others use wrong keywords or punctuation.

3. Final Answer:

   if (x > 5) { Console.WriteLine("Yes"); } -> Option D

4. Quick Check:

   Correct C# if syntax = D [OK]

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

Common Mistakes:

• Omitting parentheses around condition
• Using Python or other language syntax
• Missing braces for code block

3. What will this code print?

int x = 10;
if (x < 5) {
  Console.WriteLine("Less");
} else {
  Console.WriteLine("More or equal");
}

medium

A. Less

B. More or equal

C. Nothing

D. Error

Solution

1. Step 1: Evaluate the condition

   The condition x < 5 is false because x is 10.

2. Step 2: Determine which block runs

   Since the condition is false, the else block runs, printing "More or equal".

3. Final Answer:

   More or equal -> Option B

4. Quick Check:

   Condition false -> else runs = A [OK]

Hint: If false, else block runs [OK]

Common Mistakes:

• Thinking if block runs when false
• Ignoring else block
• Confusing < with >

4. Find the error in this code:

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

medium

A. Missing parentheses around the condition

B. Missing semicolon after if

C. Wrong keyword else

D. Variable num not declared

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 has if num > 5 { without parentheses, causing a syntax error.

3. Final Answer:

   Missing parentheses around the condition -> Option A

4. Quick Check:

   Parentheses needed in if condition = A [OK]

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

Common Mistakes:

• Forgetting parentheses in if
• Adding semicolon after if line
• Misusing else keyword

5. You want to print "Positive", "Negative", or "Zero" based on an integer n. Which code correctly uses if statements to do this?

hard

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

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

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

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

Solution

1. Step 1: Understand the logic needed

   We need to check if n is greater than 0, less than 0, or exactly 0.

2. Step 2: Analyze each option

   if (n > 0) { Console.WriteLine("Positive"); } else if (n < 0) { Console.WriteLine("Negative"); } else { Console.WriteLine("Zero"); } correctly uses if, else if, and else to cover all cases without overlap or missing conditions.

3. Final Answer:

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

4. Quick Check:

   Proper if-else chain covers all cases = B [OK]

Hint: Use if-else if-else chain for multiple conditions [OK]

Common Mistakes:

• Using separate ifs causing multiple prints
• Wrong order of conditions
• Incorrect else condition logic