Properties vs fields in C Sharp (C#) - Hands-On Comparison

Properties vs fields

📖 Scenario: Imagine you are creating a simple program to manage a book's information. You want to store the book's title and control how it is accessed and changed.

🎯 Goal: You will create a class with a field and a property, then see how to use them to get and set the book's title.

📋 What You'll Learn

Create a class called Book with a private field called _title of type string

Add a public property called Title with get and set accessors to control access to _title

Create an instance of Book and set the Title property

Print the value of the Title property

💡 Why This Matters

🌍 Real World

Properties help control how data inside objects is accessed and changed, which is important for keeping data safe and consistent in real programs.

💼 Career

Understanding properties and fields is essential for writing clean, maintainable code in C# and many other object-oriented languages.

1

Create the Book class with a private field

Create a class called Book with a private field named _title of type string.

C Sharp (C#)

class Book
{
    // Your code here
}

Hint

Use private string _title; inside the class to create the field.

2

Add a public property to access the field

Inside the Book class, add a public property called Title with get and set accessors that read from and write to the private field _title.

C Sharp (C#)

class Book
{
    private string _title;
    
    // Add the Title property below
    // Your code here
}

Hint

The property should have a get that returns _title and a set that assigns value to _title.

3

Create a Book object and set the Title property

Create an instance of the Book class named myBook and set its Title property to "C# Basics".

C Sharp (C#)

class Book
{
    private string _title;
    
    public string Title
    {
        get { return _title; }
        set { _title = value; }
    }
}

// Create myBook and set Title
// Your code here

Hint

Use new Book() to create the object and assign the title with myBook.Title = "C# Basics";.

4

Print the Title property value

Write a line to print the value of myBook.Title to the console.

C Sharp (C#)

class Book
{
    private string _title;
    
    public string Title
    {
        get { return _title; }
        set { _title = value; }
    }
}

Book myBook = new Book();
myBook.Title = "C# Basics";

// Print the title
// Your code here

Hint

Use Console.WriteLine(myBook.Title); inside the Main method to print the title.

Practice

1. What is the main difference between a field and a property in C#?

easy

A. Properties store data directly, fields control access to data.

B. Fields and properties are exactly the same in C#.

C. Fields store data directly, properties control access to data.

D. Properties can only be used in structs, fields only in classes.

Solution

1. Step 1: Understand what a field does

   A field is a variable inside a class that holds data directly.

2. Step 2: Understand what a property does

   A property provides controlled access to data, often using get and set methods.

3. Final Answer:

   Fields store data directly, properties control access to data. -> Option C

4. Quick Check:

   Field = direct data, Property = controlled access [OK]

Hint: Fields hold data; properties manage access to it. [OK]

Common Mistakes:

• Confusing fields and properties as the same.
• Thinking properties store data directly.
• Believing fields control access like properties.

2. Which of the following is the correct syntax to declare a property named Age with a private field in C#?

easy

A. int Age; int Age { get; set; }

B. private int Age; public int Age { get; set; }

C. public int age; public int Age;

D. private int age; public int Age { get { return age; } set { age = value; } }

Solution

1. Step 1: Identify private field declaration

   The private field should be lowercase (e.g., age) and declared as private int age;.

2. Step 2: Identify property syntax

   The property Age uses get and set to access the private field correctly.

3. Final Answer:

   private int age; public int Age { get { return age; } set { age = value; } } -> Option D

4. Quick Check:

   Private field + property with get/set = correct syntax [OK]

Hint: Private field lowercase, property uppercase with get/set. [OK]

Common Mistakes:

• Using same name for field and property causing errors.
• Missing get or set in property.
• Declaring fields as public when they should be private.

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

class Person {
  private string name = "Alice";
  public string Name {
    get { return name; }
    set { name = value; }
  }
}

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

medium

A. Bob

B. name

C. Alice

D. Compilation error

Solution

1. Step 1: Understand property set operation

   The line p.Name = "Bob"; calls the set accessor, changing the private field name to "Bob".

2. Step 2: Understand property get operation

   The line Console.WriteLine(p.Name); calls the get accessor, returning the updated value "Bob".

3. Final Answer:

   Bob -> Option A

4. Quick Check:

   Property set changes value, get returns updated value [OK]

Hint: Property set changes field; get returns updated value. [OK]

Common Mistakes:

• Assuming output is original field value.
• Confusing field name with property name.
• Thinking code causes compilation error.

4. Identify the error in this code snippet:

class Car {
  public int speed;
  public int Speed {
    get { return speed; }
    set { speed = value; }
  }
}

var c = new Car();
c.Speed = 50;
Console.WriteLine(c.speed);

medium

A. Accessing field directly breaks encapsulation.

B. Field and property have the same name causing conflict.

C. No error; code works fine.

D. Property must be static to access field.

Solution

1. Step 1: Check field and property names

   The field is speed and property is Speed, so no naming conflict.

2. Step 2: Analyze direct field access

   Accessing c.speed directly bypasses the property, which can break encapsulation and safety.

3. Final Answer:

   Accessing field directly breaks encapsulation. -> Option A

4. Quick Check:

   Use properties to protect data, not direct field access [OK]

Hint: Avoid direct field access; use properties for safety. [OK]

Common Mistakes:

• Thinking same names cause error (case-sensitive).
• Believing direct field access is always safe.
• Assuming property must be static.

5. You want to create a class BankAccount where the Balance can be read publicly but only changed inside the class. Which is the best way to declare Balance?

hard

A. public decimal Balance; // public field

B. private decimal balance; public decimal Balance { get; private set; }

C. public decimal Balance { private get; set; }

D. private decimal Balance; public decimal balance { get; set; }

Solution

1. Step 1: Understand access needs

   Balance should be readable publicly but only settable privately inside the class.

2. Step 2: Choose property with private set

   Using public decimal Balance { get; private set; } allows public reading but restricts setting to inside the class.

3. Final Answer:

   private decimal balance; public decimal Balance { get; private set; } -> Option B

4. Quick Check:

   Public get + private set = controlled access [OK]

Hint: Use property with private set for controlled write access. [OK]

Common Mistakes:

• Using public field exposes data to unwanted changes.
• Setting private get hides data from outside.
• Confusing field and property naming conventions.