Extension method syntax in C Sharp (C#) - Mini Project: Build & Apply

Create and Use an Extension Method in C#

📖 Scenario: Imagine you want to add a new feature to the string type in C# without changing its original code. You will create an extension method that adds a simple greeting to any string.

🎯 Goal: Build a C# program that defines an extension method called Greet for the string type. This method will return a greeting message using the original string. Then, use this method on a string variable and print the result.

📋 What You'll Learn

Create a static class called StringExtensions

Inside it, create a public static method called Greet that extends string

The Greet method should return a string formatted as "Hello, {original string}!"

Use the Greet method on a string variable called name

Print the result of calling name.Greet()

💡 Why This Matters

🌍 Real World

Extension methods let you add new features to existing types without changing their original code. This is useful when working with libraries or built-in types.

💼 Career

Many C# developers use extension methods to write cleaner, more readable code and to add helpful utilities to existing types.

1

Create a string variable

Create a string variable called name and set it to the value "Alice".

C Sharp (C#)

# Create a string variable called name and set it to "Alice"
# Your code here

Need a hint?

Use string name = "Alice"; to create the variable.

2

Create a static class for extension methods

Create a public static class called StringExtensions to hold extension methods.

C Sharp (C#)

string name = "Alice";

// Create a public static class called StringExtensions
# Your code here

Need a hint?

Use public static class StringExtensions { } to create the class.

3

Add the extension method Greet

Inside the StringExtensions class, create a public static method called Greet that extends string using the this keyword. The method should return a string formatted as "Hello, {original string}!".

C Sharp (C#)

string name = "Alice";

public static class StringExtensions
{
    // Create a public static method Greet that extends string
    // It returns "Hello, {original string}!"
    # Your code here
}

Need a hint?

Use public static string Greet(this string str) and return the greeting with $"Hello, {str}!".

4

Use the extension method and print the result

Call the Greet method on the name variable and print the result using Console.WriteLine.

C Sharp (C#)

string name = "Alice";

public static class StringExtensions
{
    public static string Greet(this string str)
    {
        return $"Hello, {str}!";
    }
}

// Call name.Greet() and print the result
# Your code here

Need a hint?

Use Console.WriteLine(name.Greet()); to print the greeting.