Ternary conditional operator in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested ternary operator

What is the output of this C# code snippet?

C Sharp (C#)

int x = 5;
int y = 10;
string result = x > y ? "x is greater" : x == y ? "x equals y" : "x is smaller";
Console.WriteLine(result);

A x is greater

B x equals y

C x is smaller

D Compilation error

💡 Hint

Remember how nested ternary operators evaluate conditions from left to right.

Since x (5) is less than y (10), the first condition (x > y) is false, so it evaluates the second ternary: x == y? which is also false, so it returns "x is smaller".

❓ Predict Output

intermediate

Ternary operator with boolean expressions

What will this code print?

C Sharp (C#)

bool isSunny = false;
bool haveUmbrella = true;
string message = isSunny ? "Go outside" : haveUmbrella ? "Take umbrella" : "Stay inside";
Console.WriteLine(message);

A Go outside

B Take umbrella

C Stay inside

D Runtime error

💡 Hint

Check the value of isSunny and then haveUmbrella.

isSunny is false, so it evaluates the second ternary. haveUmbrella is true, so it returns "Take umbrella".

❓ Predict Output

advanced

Ternary operator with different data types

What is the output of this code?

C Sharp (C#)

var value = 7;
var output = value % 2 == 0 ? "Even" : value > 5 ? 100 : 50;
Console.WriteLine(output);

A Compilation error

B Even

C 50

D 100

💡 Hint

Check the types of the values returned by the ternary operator.

The ternary operator must return the same type for both outcomes. Here, one branch returns a string and the other returns an int, causing a compilation error.

❓ Predict Output

advanced

Ternary operator with side effects

What will be printed by this code?

C Sharp (C#)

int a = 3;
int b = 4;
int result = a > b ? a++ : ++b;
Console.WriteLine($"result = {result}, a = {a}, b = {b}");

A result = 5, a = 3, b = 5

B result = 3, a = 4, b = 4

C result = 3, a = 3, b = 5

D result = 4, a = 3, b = 4

💡 Hint

Remember how post-increment and pre-increment operators work.

Since a (3) is not greater than b (4), the false branch ++b is executed. ++b increments b to 5 and returns the new value 5, which is assigned to result. a remains 3. Output: result = 5, a = 3, b = 5.

❓ Predict Output

expert

Complex nested ternary with method calls

What is the output of this code?

C Sharp (C#)

static string Check(int n) => n % 2 == 0 ? "Even" : n % 3 == 0 ? "Divisible by 3" : "Other";

Console.WriteLine(Check(9));

A Even

B Compilation error

C Other

D Divisible by 3

💡 Hint

Check the order of conditions in the nested ternary.

9 is not even, so first condition is false. Then it checks if 9 is divisible by 3, which is true, so it returns "Divisible by 3".

Practice

1. What does the ternary conditional operator condition ? value_if_true : value_if_false do in C#?

easy

A. It executes both value_if_true and value_if_false regardless of the condition.

B. It is used to declare variables in C#.

C. It only checks the condition but does not return any value.

D. It returns value_if_true if the condition is true, otherwise value_if_false.

Solution

1. Step 1: Understand the ternary operator syntax

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Determine what it returns based on the condition

   If the condition is true, it returns the first value; if false, it returns the second value.

3. Final Answer:

   It returns value_if_true if the condition is true, otherwise value_if_false. -> Option D

4. Quick Check:

   condition ? true_value : false_value = returns true_value if condition true [OK]

Hint: Remember: condition ? trueValue : falseValue returns one value [OK]

Common Mistakes:

• Thinking both values run regardless of condition
• Confusing ternary operator with if statement
• Believing it does not return a value

2. Which of the following is the correct syntax for using the ternary operator in C#?

easy

A. int result = (x > 0) : 1 ? 0;

B. int result = (x > 0) ? 1 : 0;

C. int result = (x > 0) ? {1, 0};

D. int result = (x > 0) ? 1;

Solution

1. Step 1: Review the ternary operator syntax

   The correct syntax is: condition ? value_if_true : value_if_false;

2. Step 2: Check each option for syntax correctness

   int result = (x > 0) ? 1 : 0; matches the correct syntax. Options A, B, and D have syntax errors or missing parts.

3. Final Answer:

   int result = (x > 0) ? 1 : 0; -> Option B

4. Quick Check:

   Correct ternary syntax uses ? and : in order [OK]

Hint: Syntax is: condition ? trueValue : falseValue; [OK]

Common Mistakes:

• Using curly braces instead of colon
• Swapping ? and : positions
• Omitting the false value after colon

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

int a = 5;
string result = (a % 2 == 0) ? "Even" : "Odd";
Console.WriteLine(result);

medium

A. Odd

B. Even

C. 5

D. Error

Solution

1. Step 1: Evaluate the condition (a % 2 == 0)

   Since a = 5, 5 % 2 equals 1, which is not 0, so the condition is false.

2. Step 2: Determine which value the ternary operator returns

   Because the condition is false, it returns "Odd".

3. Final Answer:

   Odd -> Option A

4. Quick Check:

   5 % 2 == 0 is false, so output is "Odd" [OK]

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

Common Mistakes:

• Assuming 5 is even
• Confusing modulus operator result
• Expecting numeric output instead of string

4. Identify the error in this C# code using the ternary operator:

int x = 10;
string output = x > 5 ? "High" "Low";
Console.WriteLine(output);

medium

A. Condition must be inside parentheses

B. Missing semicolon at the end of the line

C. Missing colon ':' between true and false values

D. Incorrect variable type for output

Solution

1. Step 1: Check ternary operator syntax in the code

   The ternary operator requires a colon ':' between the true and false values.

2. Step 2: Identify the missing colon

   The code has "High" "Low" without a colon, which causes a syntax error.

3. Final Answer:

   Missing colon ':' between true and false values -> Option C

4. Quick Check:

   condition ? trueValue : falseValue needs ':' separator [OK]

Hint: Always include ':' between true and false parts [OK]

Common Mistakes:

• Forgetting the colon ':'
• Adding extra quotes or commas
• Misplacing parentheses

5. Given a list of integers, which C# code snippet correctly uses the ternary operator to create a new list of strings labeling each number as "Positive" or "Non-positive"?

hard

A. var labels = numbers.Select(n => n > 0 ? "Positive" : "Non-positive").ToList();

B. var labels = numbers.Select(n => n > 0 ? "Positive" "Non-positive").ToList();

C. var labels = numbers.Select(n => if (n > 0) "Positive" else "Non-positive").ToList();

D. var labels = numbers.Select(n => n > 0 ? "Positive" : ).ToList();

Solution

1. Step 1: Understand the use of ternary operator inside LINQ Select

   The ternary operator must have a condition, true value, and false value separated by '?' and ':'.

2. Step 2: Check each option for correct syntax and logic

   var labels = numbers.Select(n => n > 0 ? "Positive" : "Non-positive").ToList(); correctly uses the ternary operator inside Select. Options B, C, and D have syntax errors or invalid expressions.

3. Final Answer:

   var labels = numbers.Select(n => n > 0 ? "Positive" : "Non-positive").ToList(); -> Option A

4. Quick Check:

   Correct ternary inside Select uses ? and : with both values [OK]

Hint: Use ? and : correctly inside lambda expressions [OK]

Common Mistakes:

• Omitting colon ':' in ternary operator
• Using if-else inside lambda without braces
• Leaving false value empty