Expression-bodied methods in C Sharp (C#)

Introduction

Expression-bodied methods let you write simple methods in a shorter, cleaner way using just one line.

When a method returns a single value or expression.

When you want to make your code easier to read by reducing clutter.

When the method logic is very simple, like returning a calculation or property.

When you want to write quick helper methods without full method blocks.

Syntax

C Sharp (C#)

returnType MethodName(parameters) => expression;

The => symbol means the method returns the result of the expression directly.

No need for curly braces { } or return keyword inside the method.

Examples

This method returns the square of the input number.

C Sharp (C#)

int Square(int x) => x * x;

This method returns a greeting message using the input name.

C Sharp (C#)

string Greet(string name) => $"Hello, {name}!";

This method checks if a number is even and returns true or false.

C Sharp (C#)

bool IsEven(int number) => number % 2 == 0;

Sample Program

This program defines an expression-bodied method Double that multiplies a number by 2. It then prints the result for the number 5.

C Sharp (C#)

using System;

class Program
{
    static int Double(int n) => n * 2;

    static void Main()
    {
        int value = 5;
        Console.WriteLine($"Double of {value} is {Double(value)}");
    }
}

Important Notes

Expression-bodied methods work best for simple, single-expression methods.

For more complex logic, use regular method blocks with curly braces.

Summary

Expression-bodied methods use => to return a single expression directly.

They make simple methods shorter and easier to read.

Use them when your method only needs to return one value or expression.

Practice

1. What is the main purpose of using expression-bodied methods in C#?

easy

A. To handle exceptions more efficiently

B. To declare variables with less code

C. To create classes without constructors

D. To write simple methods in a shorter and clearer way using the => syntax

Solution

1. Step 1: Understand expression-bodied methods

   Expression-bodied methods use the => symbol to return a single expression directly, making code shorter.

2. Step 2: Identify the purpose

   The main purpose is to simplify simple methods by writing them in one line with clear syntax.

3. Final Answer:

   To write simple methods in a shorter and clearer way using the => syntax -> Option D

4. Quick Check:

   Expression-bodied methods = shorter, clearer methods [OK]

Hint: Expression-bodied methods use => for short, single-expression methods [OK]

Common Mistakes:

• Confusing expression-bodied methods with variable declarations
• Thinking they handle exceptions
• Believing they create classes

2. Which of the following is the correct syntax for an expression-bodied method that returns the square of an integer n?

easy

A. public int Square(int n) => n * n;

B. public int Square(int n) { return n * n; }

C. public int Square(int n) => { return n * n; };

D. public int Square(int n) => return n * n;

Solution

1. Step 1: Recall expression-bodied method syntax

   Expression-bodied methods use => followed directly by the expression without braces or return keyword.

2. Step 2: Check each option

   public int Square(int n) => n * n; correctly uses => n * n; without braces or return. public int Square(int n) { return n * n; } uses normal method syntax. Options C and D have syntax errors.

3. Final Answer:

   public int Square(int n) => n * n; -> Option A

4. Quick Check:

   Correct syntax = public int Square(int n) => n * n; [OK]

Hint: Use => expression; without braces or return for expression-bodied methods [OK]

Common Mistakes:

• Adding braces {} around the expression
• Using return keyword with =>
• Missing semicolon at the end

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

class Program {
    static int Double(int x) => x * 2;
    static void Main() {
        Console.WriteLine(Double(5));
    }
}

medium

A. 5

B. 10

C. Syntax error

D. 0

Solution

1. Step 1: Understand the method Double

   The method Double takes an integer x and returns x multiplied by 2 using expression-bodied syntax.

2. Step 2: Calculate the output for Double(5)

   Double(5) returns 5 * 2 = 10, which is printed by Console.WriteLine.

3. Final Answer:

   10 -> Option B

4. Quick Check:

   Double(5) = 10 [OK]

Hint: Multiply input by 2 in expression-bodied method to get output [OK]

Common Mistakes:

• Confusing output with input value
• Expecting syntax error due to unfamiliar syntax
• Ignoring return value

4. Identify the error in the following expression-bodied method and choose the correct fix:

public int Add(int a, int b) => { return a + b; };

medium

A. Change => to =>> : public int Add(int a, int b) =>> a + b;

B. Add semicolon after return: public int Add(int a, int b) => { return a + b; };

C. Remove braces and return keyword: public int Add(int a, int b) => a + b;

D. No error, code is correct

Solution

1. Step 1: Analyze expression-bodied method syntax

   Expression-bodied methods must have a single expression after => without braces or return keyword.

2. Step 2: Identify the fix

   Remove braces and return keyword to fix syntax: public int Add(int a, int b) => a + b;

3. Final Answer:

   Remove braces and return keyword: public int Add(int a, int b) => a + b; -> Option C

4. Quick Check:

   Expression-bodied method = single expression after => [OK]

Hint: No braces or return with =>; just expression [OK]

Common Mistakes:

• Using braces {} with expression-bodied methods
• Including return keyword after =>
• Thinking =>> is valid syntax

5. You want to create an expression-bodied method IsEven that returns true if an integer is even, and false otherwise. Which of the following implementations is correct?

hard

A. public bool IsEven(int n) => n % 2 == 0;

B. public bool IsEven(int n) => { if (n % 2 == 0) return true; else return false; };

C. public bool IsEven(int n) => return n % 2 == 0;

D. public bool IsEven(int n) => n / 2 == 0;

Solution

1. Step 1: Understand the method goal

   The method should return true if n is even (n % 2 == 0), false otherwise.

2. Step 2: Check each option

   public bool IsEven(int n) => n % 2 == 0; correctly uses expression-bodied syntax with the expression n % 2 == 0. public bool IsEven(int n) => { if (n % 2 == 0) return true; else return false; }; uses braces and return, which is invalid for expression-bodied methods. public bool IsEven(int n) => return n % 2 == 0; incorrectly uses return keyword after =>. public bool IsEven(int n) => n / 2 == 0; incorrectly checks n / 2 == 0, which is wrong logic.

3. Final Answer:

   public bool IsEven(int n) => n % 2 == 0; -> Option A

4. Quick Check:

   IsEven uses n % 2 == 0 with => [OK]

Hint: Use expression n % 2 == 0 directly after => for boolean return [OK]

Common Mistakes:

• Using braces and return in expression-bodied methods
• Adding return keyword after =>
• Incorrect logic like n / 2 == 0