Properties vs fields in C Sharp (C#) - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a public field named 'age' of type int.

C Sharp (C#)

public class Person {
    public [1] age;
}

Drag options to blanks, or click blank then click option'

Aint

BAge

Cstring

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using a capitalized name like 'Age' as a type.

Using 'string' instead of 'int' for an age field.

Using access modifiers like 'private' instead of a type.

The field 'age' should be declared with the type int to store integer values.

2fill in blank

medium

Complete the code to declare a public property named 'Age' with get and set accessors.

C Sharp (C#)

public class Person {
    public int [1] { get; set; }
}

Drag options to blanks, or click blank then click option'

Aage

BageValue

CAGE

DAge

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'age' for a property name.

Using all uppercase 'AGE' which is uncommon.

Using a different name like 'ageValue' without reason.

Properties usually start with a capital letter, so Age is the correct property name.

3fill in blank

hard

Fix the error in the property declaration by completing the code.

C Sharp (C#)

public class Person {
    private int _age;
    public int Age {
        get { return [1]; }
        set { _age = value; }
    }
}

Drag options to blanks, or click blank then click option'

A_age

BAge

Cvalue

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the property name 'Age' inside its own getter causes recursion.

Returning 'value' inside getter is incorrect.

Using 'age' without underscore when the field is '_age'.

The getter should return the private field _age to provide the stored value.

4fill in blank

hard

Fill both blanks to create a property 'Name' with a private field '_name' and a setter that trims whitespace.

C Sharp (C#)

public class Person {
    private string [1];
    public string Name {
        get { return [2]; }
        set { [2] = value.Trim(); }
    }
}

Drag options to blanks, or click blank then click option'

A_name

BName

C_age

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using the property name 'Name' inside getter or setter causes recursion.

Using a different field name in getter and setter.

Not trimming the value in setter.

The private field is '_name' and both getter and setter use it to store and return the trimmed name.

5fill in blank

hard

Fill all three blanks to create a read-only property 'IsAdult' that returns true if 'Age' is 18 or more.

C Sharp (C#)

public class Person {
    public int Age { get; set; }
    public bool [1] {
        get { return Age [2] [3]; }
    }
}

Drag options to blanks, or click blank then click option'

AIsAdult

B>=

C18

DAge

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Age' as property name instead of 'IsAdult'.

Using '<' or '>' instead of '>='.

Comparing to a wrong number.

The property 'IsAdult' returns true when 'Age' is greater than or equal to 18.

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.