Named arguments in C Sharp (C#) - Mini Project: Build & Apply

Using Named Arguments in C#

📖 Scenario: Imagine you are creating a simple program to calculate the total price of a product after applying a discount and adding tax. You want to make your code clear by using named arguments when calling the method.

🎯 Goal: Build a C# program that defines a method with multiple parameters and calls it using named arguments to improve readability.

📋 What You'll Learn

Create a method called CalculateTotalPrice with parameters price, discount, and tax.

Create variables for price, discount, and tax with exact values.

Call CalculateTotalPrice using named arguments in a different order than the method definition.

Print the result of the method call.

💡 Why This Matters

🌍 Real World

Named arguments make your code easier to read and understand, especially when methods have many parameters.

💼 Career

Using named arguments is a common practice in professional C# development to improve code clarity and reduce errors.

1

Create variables for price, discount, and tax

Create three variables: price with value 100.0, discount with value 0.1, and tax with value 0.05.

C Sharp (C#)

# Your code here

Hint

Use double type for the variables and assign the exact values.

2

Define the CalculateTotalPrice method

Define a method called CalculateTotalPrice that takes three double parameters: price, discount, and tax. The method should return a double representing the final price after applying discount and adding tax.

C Sharp (C#)

double price = 100.0;
double discount = 0.1;
double tax = 0.05;

// Your code here

Hint

Calculate discounted price first, then add tax, and return the final value.

3

Call CalculateTotalPrice using named arguments

Call the method CalculateTotalPrice using named arguments in this order: tax, price, and discount. Store the result in a variable called finalPrice.

C Sharp (C#)

double price = 100.0;
double discount = 0.1;
double tax = 0.05;

double CalculateTotalPrice(double price, double discount, double tax)
{
    double discountedPrice = price - (price * discount);
    double totalPrice = discountedPrice + (discountedPrice * tax);
    return totalPrice;
}

// Your code here

Hint

Use the syntax parameterName: value to pass named arguments in any order.

4

Print the final price

Print the value of the variable finalPrice using Console.WriteLine.

C Sharp (C#)

double price = 100.0;
double discount = 0.1;
double tax = 0.05;

double CalculateTotalPrice(double price, double discount, double tax)
{
    double discountedPrice = price - (price * discount);
    double totalPrice = discountedPrice + (discountedPrice * tax);
    return totalPrice;
}

double finalPrice = CalculateTotalPrice(tax: tax, price: price, discount: discount);

// Your code here

Hint

Use Console.WriteLine(finalPrice); to print the result.

Practice

1. What is the main benefit of using named arguments in C#?

easy

A. It makes the program run faster.

B. You can specify which parameter gets which value by name, improving readability.

C. It allows you to skip parameters without default values.

D. It automatically converts data types.

Solution

1. Step 1: Understand named arguments purpose

   Named arguments let you assign values to parameters by their names instead of relying on order.

2. Step 2: Identify the benefit

   This makes code easier to read and understand because you see which value goes to which parameter.

3. Final Answer:

   You can specify which parameter gets which value by name, improving readability. -> Option B

4. Quick Check:

   Named arguments improve readability = A [OK]

Hint: Named arguments improve code clarity by naming parameters [OK]

Common Mistakes:

• Thinking named arguments speed up execution
• Assuming named arguments skip required parameters
• Believing named arguments convert types automatically

2. Which of the following is the correct syntax to call a method PrintInfo with named arguments name and age?

easy

A. PrintInfo(name => "Alice", age => 30);

B. PrintInfo("Alice": name, 30: age);

C. PrintInfo(name = "Alice", age = 30);

D. PrintInfo(name: "Alice", age: 30);

Solution

1. Step 1: Recall named argument syntax

   In C#, named arguments use the format parameterName: value.

2. Step 2: Check each option

   PrintInfo(name: "Alice", age: 30); uses correct syntax. Options A, B, and C use invalid syntax for named arguments.

3. Final Answer:

   PrintInfo(name: "Alice", age: 30); -> Option D

4. Quick Check:

   Named argument syntax = parameterName: value [OK]

Hint: Use colon ':' between parameter and value for named arguments [OK]

Common Mistakes:

• Using '=' instead of ':' for named arguments
• Placing value before parameter name
• Using '=>' instead of ':'

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

void ShowDetails(string name, int age) {
    Console.WriteLine($"Name: {name}, Age: {age}");
}

ShowDetails(age: 25, name: "Bob");

medium

A. Compilation error due to argument order

B. Name: 25, Age: Bob

C. Name: Bob, Age: 25

D. Runtime error

Solution

1. Step 1: Understand named argument order flexibility

   Named arguments allow passing parameters in any order by specifying names explicitly.

2. Step 2: Analyze the call

   The call uses age: 25 first and name: "Bob" second, which is valid and assigns correctly.

3. Final Answer:

   Name: Bob, Age: 25 -> Option C

4. Quick Check:

   Named arguments allow any order = C [OK]

Hint: Named arguments can be in any order if names are used [OK]

Common Mistakes:

• Assuming positional order is required with named arguments
• Confusing parameter names and values
• Expecting errors from reversed argument order

4. Identify the error in this method call:

void Display(string title, int count) { }

Display(count: 5, "Hello");

medium

A. Positional argument cannot follow named argument.

B. Missing semicolon after method call.

C. Parameter names are incorrect.

D. No error, code is correct.

Solution

1. Step 1: Recall argument order rules

   In C#, positional arguments must come before any named arguments.

2. Step 2: Analyze the call

   The call uses a named argument count: 5 first, then a positional argument "Hello", which is invalid.

3. Final Answer:

   Positional argument cannot follow named argument. -> Option A

4. Quick Check:

   Positional before named = B [OK]

Hint: Always put positional arguments before named ones [OK]

Common Mistakes:

• Placing positional arguments after named arguments
• Ignoring argument order rules
• Assuming named arguments can be anywhere

5. Given the method:

void Configure(string mode, int timeout = 30, bool verbose = false) { }

Which call correctly uses named arguments to set verbose to true and keep default timeout?

hard

A. Configure("fast", verbose: true);

B. Configure(verbose: true, "fast");

C. Configure(timeout: 30, "fast", verbose: true);

D. Configure("fast", true);

Solution

1. Step 1: Understand default parameters and named arguments

   Default parameters can be skipped if not specified. Named arguments let you set specific parameters by name.

2. Step 2: Analyze each call

   Configure("fast", verbose: true); sets mode positionally and verbose by name, skipping timeout to use default. Configure(verbose: true, "fast"); has positional after named (invalid). Configure(timeout: 30, "fast", verbose: true); mixes positional and named incorrectly. Configure("fast", true); sets verbose positionally, which is wrong type.

3. Final Answer:

   Configure("fast", verbose: true); -> Option A

4. Quick Check:

   Named arguments skip defaults correctly = A [OK]

Hint: Use named arguments to skip default parameters safely [OK]

Common Mistakes:

• Placing positional arguments after named arguments
• Passing wrong types positionally
• Trying to set named arguments before positional ones