Comparison operators in C Sharp (C#) - Mini Project: Build & Apply

Comparison operators

📖 Scenario: You are creating a simple program to compare ages of two friends to see who is older.

🎯 Goal: Build a program that stores two ages, compares them using comparison operators, and prints the results.

📋 What You'll Learn

Create two integer variables with exact ages

Create a boolean variable to store the comparison result

Use comparison operators to compare the ages

Print the comparison results exactly as specified

💡 Why This Matters

🌍 Real World

Comparing values is common in programs that make decisions, like checking user age for access or sorting data.

💼 Career

Understanding comparison operators is essential for writing conditions and logic in any software development job.

1

Create age variables

Create two integer variables called ageAlice and ageBob with values 25 and 30 respectively.

C Sharp (C#)

// Your code here

Hint

Use int to declare the variables and assign the exact values.

2

Create comparison variables

Create two boolean variables called isAliceOlder and isBobOlder without assigning values yet.

C Sharp (C#)

int ageAlice = 25;
int ageBob = 30;
// Your code here

Hint

Declare boolean variables using bool keyword.

3

Compare ages using comparison operators

Assign isAliceOlder to the result of ageAlice > ageBob and isBobOlder to the result of ageBob > ageAlice.

C Sharp (C#)

int ageAlice = 25;
int ageBob = 30;
bool isAliceOlder;
bool isBobOlder;
// Your code here

Hint

Use the greater than operator > to compare the ages.

4

Print the comparison results

Print the values of isAliceOlder and isBobOlder using Console.WriteLine exactly as shown: "Is Alice older? {isAliceOlder}" and "Is Bob older? {isBobOlder}".

C Sharp (C#)

int ageAlice = 25;
int ageBob = 30;
bool isAliceOlder = ageAlice > ageBob;
bool isBobOlder = ageBob > ageAlice;
// Your code here

Hint

Use Console.WriteLine with string interpolation $"...{variable}..." to print the results.

Practice

1. Which of the following comparison operators checks if two values are equal in C#?

easy

A. >

B. =

C. !=

D. ==

Solution

1. Step 1: Understand the equality operator

   The operator == is used to check if two values are equal in C#.

2. Step 2: Differentiate from assignment and other operators

   = is for assignment, != checks inequality, and > checks if left is greater than right.

3. Final Answer:

   == -> Option D

4. Quick Check:

   Equality operator = == [OK]

Hint: Use double equals (==) to check equality, not single equals [OK]

Common Mistakes:

• Using single equals (=) instead of double equals (==)
• Confusing != with == operator
• Using > when checking equality

2. Which of the following is the correct syntax to check if variable x is not equal to 10 in C#?

easy

A. if (x != 10)

B. if (x =! 10)

C. if (x = 10)

D. if (x ==! 10)

Solution

1. Step 1: Identify the correct not equal operator

   The operator != is used to check if two values are not equal in C#.

2. Step 2: Check syntax correctness

   if (x != 10) is correct syntax. The others have incorrect operator placement or use assignment instead of comparison.

3. Final Answer:

   if (x != 10) -> Option A

4. Quick Check:

   Not equal operator = != [OK]

Hint: Use != to check not equal, watch operator order carefully [OK]

Common Mistakes:

• Writing =! instead of != operator
• Using single = instead of comparison operator
• Combining == and ! incorrectly

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

int a = 5;
int b = 8;
Console.WriteLine(a > b);

medium

A. 5

B. True

C. False

D. 8

Solution

1. Step 1: Compare values of a and b

   Variable a is 5 and b is 8. The expression a > b checks if 5 is greater than 8.

2. Step 2: Evaluate the comparison

   Since 5 is not greater than 8, the expression returns false.

3. Final Answer:

   False -> Option C

4. Quick Check:

   5 > 8 = False [OK]

Hint: Compare values carefully; 5 is not greater than 8 [OK]

Common Mistakes:

• Assuming 5 > 8 is true
• Confusing output with variable values
• Expecting numeric output instead of boolean

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

int x = 10;
if (x = 5)
{
    Console.WriteLine("Equal");
}

medium

A. Using assignment (=) instead of comparison (==) in if condition

B. Missing semicolon after if statement

C. Incorrect variable declaration

D. Console.WriteLine syntax error

Solution

1. Step 1: Check the if condition syntax

   The condition uses = which assigns 5 to x instead of comparing.

2. Step 2: Correct operator usage

   Use == to compare values in conditions, so it should be if (x == 5).

3. Final Answer:

   Using assignment (=) instead of comparison (==) in if condition -> Option A

4. Quick Check:

   Comparison needs ==, not = [OK]

Hint: Use double equals (==) in conditions, not single equals (=) [OK]

Common Mistakes:

• Using = instead of == in if conditions
• Forgetting to use parentheses in if
• Misunderstanding assignment vs comparison

5. You want to check if a number n is between 10 and 20 inclusive in C#. Which condition correctly uses comparison operators?

hard

A. if (n > 10 || n < 20)

B. if (n >= 10 && n <= 20)

C. if (10 <= n <= 20)

D. if (n == 10 && n == 20)

Solution

1. Step 1: Understand range checking in C#

   C# does not support chained comparisons like 10 <= n <= 20. You must combine two comparisons with logical AND.

2. Step 2: Analyze each option

   if (n >= 10 && n <= 20) uses n >= 10 && n <= 20, which correctly checks if n is between 10 and 20 inclusive. if (10 <= n <= 20) is invalid syntax. if (n > 10 || n < 20) uses OR which is incorrect for range. if (n == 10 && n == 20) checks if n equals both 10 and 20 simultaneously, which is impossible.

3. Final Answer:

   if (n >= 10 && n <= 20) -> Option B

4. Quick Check:

   Use && to combine comparisons for ranges [OK]

Hint: Use && to combine two comparisons for range checks [OK]

Common Mistakes:

• Trying chained comparisons like 10 <= n <= 20
• Using || instead of && for range
• Checking impossible conditions with == for both ends