Attribute declaration syntax in C Sharp (C#) - Mini Project: Build & Apply

Attribute declaration syntax

📖 Scenario: You are creating a simple program to mark classes and methods with custom notes using attributes. Attributes are special tags that add extra information to your code, like labels on a box.

🎯 Goal: Learn how to declare and use attributes in C# by creating a custom attribute and applying it to a class and a method.

📋 What You'll Learn

Declare a custom attribute class called InfoAttribute with a string property Description.

Create a class called Calculator and apply the InfoAttribute with a description.

Add a method Add inside Calculator and apply the InfoAttribute with a description.

Print the descriptions stored in the attributes for the class and method.

💡 Why This Matters

🌍 Real World

Attributes are used in real-world C# programs to add metadata for tools, frameworks, and libraries. For example, marking methods as test cases or marking classes for serialization.

💼 Career

Understanding attribute declaration and usage is important for C# developers working with frameworks like ASP.NET, Entity Framework, or writing reusable libraries.

1

Declare the InfoAttribute class

Declare a public class called InfoAttribute that inherits from System.Attribute. Add a public string property called Description with a getter and setter.

C Sharp (C#)

# Your code here

Need a hint?

Remember, attributes in C# inherit from System.Attribute. Use public string Description { get; set; } to create the property.

2

Create the Calculator class and apply InfoAttribute

Create a public class called Calculator. Apply the InfoAttribute to it with the description set to "Performs basic math operations".

C Sharp (C#)

using System;

public class InfoAttribute : Attribute
{
    public string Description { get; set; }
}

// Your code here

Need a hint?

Use square brackets [] to apply the attribute above the class. Set the Description property inside the parentheses.

3

Add Add method with InfoAttribute

Inside the Calculator class, add a public method called Add that takes two integers a and b and returns their sum. Apply the InfoAttribute to this method with the description "Adds two numbers".

C Sharp (C#)

using System;

public class InfoAttribute : Attribute
{
    public string Description { get; set; }
}

[Info(Description = "Performs basic math operations")]
public class Calculator
{
    // Your code here
}

Need a hint?

Apply the attribute above the method. The method should return the sum of a and b.

4

Print attribute descriptions for class and method

Write code in Main to get the InfoAttribute from the Calculator class and its Add method. Print the Description property of both attributes.

C Sharp (C#)

using System;

public class InfoAttribute : Attribute
{
    public string Description { get; set; }
}

[Info(Description = "Performs basic math operations")]
public class Calculator
{
    [Info(Description = "Adds two numbers")]
    public int Add(int a, int b)
    {
        return a + b;
    }
}

class Program
{
    static void Main()
    {
        // Your code here
    }
}

Need a hint?

Use Attribute.GetCustomAttribute to get the attribute from the class and method. Then print their Description.