Auto-implemented properties in C Sharp (C#) - Mini Project: Build & Apply

Auto-implemented properties

📖 Scenario: You are creating a simple program to store information about a book in a library system.

🎯 Goal: Build a class with auto-implemented properties to hold the book's title and author, then create an object and display its details.

📋 What You'll Learn

Create a class named Book with two auto-implemented properties: Title and Author, both of type string.

Create an instance of the Book class named myBook.

Set the Title property of myBook to "The Great Gatsby".

Set the Author property of myBook to "F. Scott Fitzgerald".

Print the book details in the format: Title: The Great Gatsby, Author: F. Scott Fitzgerald.

💡 Why This Matters

🌍 Real World

Auto-implemented properties are used to quickly create simple classes that hold data, like records of books, customers, or products.

💼 Career

Understanding auto-implemented properties is essential for C# developers to write clean and efficient code for data models in applications.

1

Create the Book class with auto-implemented properties

Create a class called Book with two auto-implemented properties: Title and Author, both of type string.

C Sharp (C#)

// Your code here

Hint

Auto-implemented properties use { get; set; } without extra code inside.

2

Create an instance of the Book class

Create an instance of the Book class named myBook.

C Sharp (C#)

public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
}

// Your code here

Hint

Use new Book() to create the object.

3

Set the Title and Author properties

Set the Title property of myBook to "The Great Gatsby" and the Author property to "F. Scott Fitzgerald".

C Sharp (C#)

public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
}

Book myBook = new Book();
// Your code here

Hint

Assign values directly to the properties using the dot . operator.

4

Print the book details

Write a Console.WriteLine statement to print the book details in the format: Title: The Great Gatsby, Author: F. Scott Fitzgerald.

C Sharp (C#)

public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
}

Book myBook = new Book();
myBook.Title = "The Great Gatsby";
myBook.Author = "F. Scott Fitzgerald";

// Your code here

Hint

Use Console.WriteLine with an interpolated string $"..." to include property values.

Practice

1. What is the main advantage of using auto-implemented properties in C#?

easy

A. They replace constructors for initializing objects.

B. They allow methods to be called without creating an object.

C. They automatically create a private backing field without extra code.

D. They enable multiple inheritance in classes.

Solution

1. Step 1: Understand what auto-implemented properties do

   Auto-implemented properties create a hidden private field automatically to store data without writing extra code.

2. Step 2: Compare with other options

   Options A, B, and C describe unrelated features: constructors, method calls, and inheritance, which are not related to auto-implemented properties.

3. Final Answer:

   They automatically create a private backing field without extra code. -> Option C

4. Quick Check:

   Auto-implemented properties = hidden backing field [OK]

Hint: Auto-properties hide the field; no manual variable needed [OK]

Common Mistakes:

• Confusing properties with methods
• Thinking auto-properties replace constructors
• Believing they enable inheritance

2. Which of the following is the correct syntax for an auto-implemented property named Age of type int?

easy

A. public int Age { get; set; }

B. public int Age() { get; set; }

C. public int Age { get get; set; }

D. public int Age get; set;

Solution

1. Step 1: Identify correct property syntax

   The correct syntax for an auto-implemented property uses curly braces with get; and set; inside: public int Age { get; set; }.

2. Step 2: Check other options for syntax errors

   public int Age() { get; set; } uses parentheses which are for methods, not properties. public int Age { get get; set; } repeats get incorrectly. public int Age get; set; misses braces and semicolons are misplaced.

3. Final Answer:

   public int Age { get; set; } -> Option A

4. Quick Check:

   Property syntax = { get; set; } [OK]

Hint: Properties use braces { } with get; and set; inside [OK]

Common Mistakes:

• Using parentheses instead of braces
• Writing get or set twice
• Omitting braces or semicolons

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

class Person {
    public string Name { get; set; }
}

var p = new Person();
p.Name = "Alice";
Console.WriteLine(p.Name);

medium

A. null

B. Alice

C. Name

D. Compilation error

Solution

1. Step 1: Understand property assignment

   The property Name is auto-implemented, so it stores the value "Alice" when assigned.

2. Step 2: Output the property value

   When Console.WriteLine(p.Name); runs, it prints the stored string "Alice".

3. Final Answer:

   Alice -> Option B

4. Quick Check:

   Property stores "Alice" = output "Alice" [OK]

Hint: Auto-properties store and return assigned values [OK]

Common Mistakes:

• Expecting property name instead of value
• Thinking default null prints as text
• Assuming syntax error without reason

4. Identify the error in this code snippet:

class Car {
    public int Speed { get; private set; }
}

var c = new Car();
c.Speed = 100;
Console.WriteLine(c.Speed);

medium

A. No error; code runs and prints 100.

B. Missing semicolon after property declaration.

C. Property 'Speed' must be static.

D. Cannot assign to 'Speed' because the setter is private.

Solution

1. Step 1: Analyze property access modifiers

   The property Speed has a private setter, so it cannot be assigned outside the class.

2. Step 2: Check assignment in main code

   The line c.Speed = 100; tries to assign from outside, causing a compile error.

3. Final Answer:

   Cannot assign to 'Speed' because the setter is private. -> Option D

4. Quick Check:

   Private setter blocks external assignment [OK]

Hint: Private set means only class can assign property [OK]

Common Mistakes:

• Ignoring setter access level
• Assuming public setter by default
• Confusing property with field

5. You want to create a class Book with an auto-implemented property Title that can be read publicly but only set privately within the class. Which code snippet correctly implements this?

hard

A. public class Book { public string Title { get; private set; } }

B. public class Book { private string Title { get; set; } }

C. public class Book { public string Title { private get; set; } }

D. public class Book { public string Title { get; set; private } }

Solution

1. Step 1: Understand access modifiers for properties

   To allow public reading but private setting, the getter must be public and setter private: get; private set;.

2. Step 2: Check each option's syntax and access

   public class Book { public string Title { get; private set; } } correctly uses public string Title { get; private set; }. public class Book { private string Title { get; set; } } makes the whole property private. public class Book { public string Title { private get; set; } } incorrectly places private before get. public class Book { public string Title { get; set; private } } has invalid syntax.

3. Final Answer:

   public class Book { public string Title { get; private set; } } -> Option A

4. Quick Check:

   Public get + private set = public class Book { public string Title { get; private set; } } [OK]

Hint: Use 'get; private set;' for public read, private write [OK]

Common Mistakes:

• Placing private before get instead of set
• Making whole property private
• Incorrect syntax order for accessors