Read-only and write-only properties in C Sharp (C#) - Mini Project: Build & Apply

Read-only and Write-only Properties in C#

📖 Scenario: You are creating a simple user profile system where some information should be visible but not changeable, and some information should be set but not visible directly.

🎯 Goal: Build a C# class with a read-only property and a write-only property to control access to user data.

📋 What You'll Learn

Create a class called UserProfile

Add a private string field called username

Add a private string field called password

Create a read-only property Username that returns the username

Create a write-only property Password that sets the password

Create a method DisplayInfo that prints the username and a message about the password

💡 Why This Matters

🌍 Real World

Read-only and write-only properties are used in real applications to protect sensitive data like usernames and passwords, ensuring users can see or set data only in allowed ways.

💼 Career

Understanding property access control is important for software developers to write secure and maintainable code, especially when handling user data.

1

Create the UserProfile class with private fields

Create a class called UserProfile with two private string fields: username and password. Initialize username to "Alice" and password to "" (empty string).

C Sharp (C#)

class UserProfile
{
    // Your code here
}

Hint

Use private string username = "Alice"; and private string password = ""; inside the class.

2

Add read-only and write-only properties

Inside the UserProfile class, add a read-only property called Username that returns the username field, and a write-only property called Password that sets the password field.

C Sharp (C#)

class UserProfile
{
    private string username = "Alice";
    private string password = "";

    // Your code here
}

Hint

Use public string Username { get { return username; } } and public string Password { set { password = value; } }.

3

Add a method to display user info

Add a public method called DisplayInfo inside UserProfile that prints the username and the message "Password is set" if the password is not empty, otherwise "Password is not set".

C Sharp (C#)

class UserProfile
{
    private string username = "Alice";
    private string password = "";

    public string Username
    {
        get { return username; }
    }

    public string Password
    {
        set { password = value; }
    }

    // Your code here
}

Hint

Use System.Console.WriteLine to print the username and check if password is empty or not.

4

Create an instance, set password, and display info

In the Main method, create an instance of UserProfile called user. Set the Password property to "secret123". Then call DisplayInfo() on user to print the username and password status.

C Sharp (C#)

class UserProfile
{
    private string username = "Alice";
    private string password = "";

    public string Username
    {
        get { return username; }
    }

    public string Password
    {
        set { password = value; }
    }

    public void DisplayInfo()
    {
        System.Console.WriteLine($"Username: {username}");
        if (password != "")
            System.Console.WriteLine("Password is set");
        else
            System.Console.WriteLine("Password is not set");
    }
}

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

Hint

Create UserProfile user = new UserProfile();, set user.Password = "secret123";, then call user.DisplayInfo();.

Practice

1.

Which statement correctly describes a read-only property in C#?

easy

A. It has only a set accessor and no get accessor.

B. It has only a get accessor and no set accessor.

C. It has both get and set accessors.

D. It has no accessors at all.

Solution

1. Step 1: Understand property accessors

   A property with only a get accessor allows reading but not writing.

2. Step 2: Identify read-only property

   Read-only properties have no set accessor, so they cannot be assigned a value.

3. Final Answer:

   It has only a get accessor and no set accessor. -> Option B

4. Quick Check:

   Read-only = get only [OK]

Hint: Read-only means only get accessor present [OK]

Common Mistakes:

• Confusing read-only with write-only properties
• Thinking both get and set are needed for read-only
• Assuming no accessors means read-only

2.

Which of the following is the correct syntax for a write-only property named Password in C#?

public string Password { ? }

easy

A. set { _password = value; }

B. get { return _password; }

C. get; set;

D. private get; public set;

Solution

1. Step 1: Identify write-only property syntax

   A write-only property has only a set accessor to allow writing but no reading.

2. Step 2: Match syntax to write-only

   set { _password = value; } shows only a set accessor with assignment, which is correct for write-only.

3. Final Answer:

   set { _password = value; } -> Option A

4. Quick Check:

   Write-only = set only [OK]

Hint: Write-only means only set accessor present [OK]

Common Mistakes:

• Using get accessor in write-only property
• Using both get and set for write-only
• Incorrect accessor visibility modifiers

3.

What will be the output of the following C# code?

class User {
    private string _name = "Alice";
    public string Name { get { return _name; } }
}

var user = new User();
Console.WriteLine(user.Name);

medium

A. Compilation error

B. null

C. Runtime error

D. Alice

Solution

1. Step 1: Analyze the property

   The Name property is read-only with a get accessor returning "Alice".

2. Step 2: Check output of Console.WriteLine

   Calling user.Name returns "Alice", so it prints "Alice".

3. Final Answer:

   Alice -> Option D

4. Quick Check:

   Read-only property returns stored value [OK]

Hint: Read-only property returns stored value when accessed [OK]

Common Mistakes:

• Expecting a compilation error due to missing set
• Thinking write-only properties can be read
• Confusing private field with property access

4.

Identify the error in this C# code snippet:

class Account {
    private string _pin;
    public string Pin {
        get { return _pin; }
        set { _pin = value; }
    }
}

var acc = new Account();
acc.Pin = "1234";
Console.WriteLine(acc.Pin);

The goal is to make Pin write-only.

medium

A. The private field _pin should be public.

B. The set accessor should return a value.

C. The property has both get and set accessors, so it is not write-only.

D. The property should be static.

Solution

1. Step 1: Check property accessors

   The property has both get and set accessors, allowing reading and writing.

2. Step 2: Understand write-only requirement

   Write-only properties must have only a set accessor and no get accessor.

3. Final Answer:

   The property has both get and set accessors, so it is not write-only. -> Option C

4. Quick Check:

   Write-only = set only, no get [OK]

Hint: Write-only means no get accessor allowed [OK]

Common Mistakes:

• Leaving both get and set for write-only
• Changing field visibility instead of property
• Expecting set to return a value

5.

You want to create a class Secret that stores a string value. The value should be settable but never readable from outside the class. Inside the class, you want to log the value whenever it is set. Which property implementation achieves this?

hard

A. public string Data { set { Console.WriteLine(value); _data = value; } }

B. public string Data { get { return _data; } private set { _data = value; } }

C. public string Data { get; set; }

D. public string Data { private get; set { Console.WriteLine(value); _data = value; } }

Solution

1. Step 1: Identify write-only property with logging

   The property must have only a set accessor to be write-only and log the value when set.

2. Step 2: Check each option

   public string Data { set { Console.WriteLine(value); _data = value; } } has only a set accessor that logs and assigns the value, matching requirements.

3. Final Answer:

   public string Data { set { Console.WriteLine(value); _data = value; } } -> Option A

4. Quick Check:

   Write-only with logging in set accessor [OK]

Hint: Write-only property has only set accessor with logging code [OK]

Common Mistakes:

• Adding get accessor making property readable
• Using private get instead of no get
• Not logging inside set accessor