Access modifiers (public, private, internal) in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the field accessible from anywhere.

C Sharp (C#)

class MyClass {
    [1] int number;
}

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

Aprivate

Bprotected

Cpublic

Dinternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using private makes the member accessible only inside the class.

Internal restricts access to the same assembly.

The public modifier makes the member accessible from any other code.

2fill in blank

medium

Complete the code to restrict access to the method only within the same assembly.

C Sharp (C#)

class Calculator {
    [1] int Add(int a, int b) {
        return a + b;
    }
}

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

Ainternal

Bpublic

Cprivate

Dprotected

Attempts:

3 left

💡 Hint

Common Mistakes

Using private restricts access only to the class itself.

Public allows access from anywhere, which is too broad here.

The internal modifier restricts access to the same assembly.

3fill in blank

hard

Complete the code to make the field accessible only inside the class.

C Sharp (C#)

class Person {
    [1] string name;

    public Person(string name) {
        this.name = name;
    }
}

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

Aprivate

Bpublic

Cinternal

Dprotected

Attempts:

3 left

💡 Hint

Common Mistakes

Using public exposes the field to all classes.

Internal allows access from the same assembly, which is broader than needed.

The private modifier restricts access to inside the class only, which is correct for encapsulation.

4fill in blank

hard

Fill in the blank to declare a method accessible only within the class and its derived classes, but not outside.

C Sharp (C#)

using System;

class Animal {
    [1] void Speak() {
        Console.WriteLine("Animal sound");
    }
}

class Dog : Animal {
    public void Bark() {
        Speak();
    }
}

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

Aprivate

Bprotected

Cpublic

Dinternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using private restricts access only to the class itself.

Public allows access from anywhere, which is too broad.

The protected modifier allows access inside the class and its subclasses, but not outside.

5fill in blank

hard

Fill all three blanks to create a class with a private field, an internal method, and a public method.

C Sharp (C#)

class BankAccount {
    [1] decimal balance;

    [2] void UpdateBalance(decimal amount) {
        balance += amount;
    }

    [3] decimal GetBalance() {
        return balance;
    }
}

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

Aprivate

Binternal

Cpublic

Dprotected

Attempts:

3 left

💡 Hint

Common Mistakes

Making balance public exposes it directly.

Using private for UpdateBalance restricts it too much.

Using internal for GetBalance limits access unnecessarily.

The field is private to hide it, the update method is internal to allow access within the assembly, and the getter is public to allow access from anywhere.

Practice

1.

Which access modifier allows a class member to be accessed from any other code in the same project or assembly?

easy

A. internal

B. private

C. public

D. protected

Solution

1. Step 1: Understand the meaning of internal

   The internal modifier allows access within the same assembly or project but not outside it.

2. Step 2: Compare with other modifiers

   private restricts access to the same class only, public allows access from anywhere, and protected allows access in derived classes.

3. Final Answer:

   internal -> Option A

4. Quick Check:

   Access inside project = internal [OK]

Hint: Internal means accessible only within the same project [OK]

Common Mistakes:

• Confusing internal with public
• Thinking private allows access outside class
• Mixing protected with internal

2.

Which of the following is the correct way to declare a private integer field named count in a class?

?

easy

A. internal count int;

B. int private count;

C. public int count;

D. private int count;

Solution

1. Step 1: Recall correct syntax for access modifiers

   The access modifier comes first, then the type, then the variable name.

2. Step 2: Check each option's order and keywords

   private int count; follows correct order: private int count;. Others have incorrect order or missing type.

3. Final Answer:

   private int count; -> Option D

4. Quick Check:

   Access modifier + type + name [OK]

Hint: Access modifier always comes before type in declaration [OK]

Common Mistakes:

• Placing access modifier after type
• Omitting the type
• Using invalid order of keywords

3.

Consider the following code snippet:

class MyClass {
    private int secret = 42;
    public int GetSecret() {
        return secret;
    }
}

MyClass obj = new MyClass();
Console.WriteLine(obj.secret);

What will happen when this code runs?

medium

A. Runtime error: NullReferenceException

B. It prints 42

C. Compilation error: 'secret' is inaccessible due to its protection level

D. It prints 0

Solution

1. Step 1: Identify access modifier of 'secret'

   The field secret is declared private, so it cannot be accessed outside MyClass.

2. Step 2: Check code accessing 'secret'

   The code tries to access obj.secret outside the class, which is not allowed and causes a compile-time error.

3. Final Answer:

   Compilation error: 'secret' is inaccessible due to its protection level -> Option C

4. Quick Check:

   Private fields cannot be accessed outside class [OK]

Hint: Private members cannot be accessed from outside their class [OK]

Common Mistakes:

• Assuming private fields are accessible outside class
• Confusing runtime errors with compile errors
• Thinking public methods expose private fields directly

4.

Given this code snippet, identify the error and fix it:

class Sample {
    internal int value;
}

class Test {
    void Show() {
        Sample s = new Sample();
        Console.WriteLine(s.value);
    }
}

Assuming these classes are in different projects, what is the problem?

medium

A. No error, code runs fine

B. Error: 'value' is inaccessible due to protection level; fix by changing 'internal' to 'public'

C. Error: 'value' must be private; fix by changing 'internal' to 'private'

D. Error: 'value' must be static; fix by adding 'static' keyword

Solution

1. Step 1: Understand 'internal' access modifier scope

   internal allows access only within the same project or assembly.

2. Step 2: Check class locations

   Since Sample and Test are in different projects, Test cannot access internal members of Sample.

3. Step 3: Fix the access level

   Changing value to public allows access from other projects.

4. Final Answer:

   Error: 'value' is inaccessible due to protection level; fix by changing 'internal' to 'public' -> Option B

5. Quick Check:

   Internal = same project only; public = accessible everywhere [OK]

Hint: Internal limits access to same project; use public for cross-project [OK]

Common Mistakes:

• Assuming internal allows cross-project access
• Changing internal to private incorrectly
• Confusing static with access modifiers

5.

You have a class library project with a class Helper that has a method Calculate() marked as internal. You want to allow another project in the same solution to use Calculate() without making it public. What is the best way to achieve this?

hard

A. Use the InternalsVisibleTo attribute to expose internal members to the other project

B. Change the method to public

C. Change the method to private and create a public wrapper

D. Move the method to the other project

Solution

1. Step 1: Understand internal and project boundaries

   internal restricts access to the same assembly, so other projects cannot access it by default.

2. Step 2: Use InternalsVisibleTo attribute

   This attribute allows you to specify friend assemblies that can access internal members without making them public.

3. Step 3: Evaluate other options

   Changing to public exposes to all, private hides too much, moving method is impractical.

4. Final Answer:

   Use the InternalsVisibleTo attribute to expose internal members to the other project -> Option A

5. Quick Check:

   InternalsVisibleTo grants internal access to specific projects [OK]

Hint: Use InternalsVisibleTo to share internal members across projects [OK]

Common Mistakes:

• Making method public unnecessarily
• Thinking private allows cross-project access
• Moving code instead of using attributes