Read-only and write-only properties in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a read-only property

What is the output of this C# code snippet?

C Sharp (C#)

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

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

A Alice

B null

C Compilation error

D Empty string

💡 Hint

Look at the get accessor and the initial value of the private field.

The property 'Name' has only a get accessor returning the private field 'name' which is initialized to "Alice". So printing p.Name outputs "Alice".

❓ Predict Output

intermediate

Effect of write-only property

What happens when you try to read a write-only property in this code?

C Sharp (C#)

class Secret {
    private string code;
    public string Code {
        set { code = value; }
    }
}

var s = new Secret();
s.Code = "1234";
Console.WriteLine(s.Code);

A Compilation error

B null

C Runtime exception

D 1234

💡 Hint

Check if the property has a get accessor.

The property 'Code' has only a set accessor and no get accessor. Trying to read s.Code causes a compilation error.

🧠 Conceptual

advanced

Understanding read-only auto-properties

Which statement about this code is true?

C Sharp (C#)

class Data {
    public int Value { get; } = 10;
}

var d = new Data();
d.Value = 20;

A Runtime exception when assigning 20

B Value is updated to 20 successfully

C Compilation error because Value has no set accessor

D Value remains 10 but no error

💡 Hint

Check if the property allows assignment outside the constructor.

The property 'Value' has only a get accessor and is initialized inline. Assigning to it outside the constructor causes a compilation error.

❓ Predict Output

advanced

Behavior of write-only property with backing field

What is the output of this code?

C Sharp (C#)

class Box {
    private int size = 5;
    public int Size {
        set { size = value; }
    }
    public int GetSize() => size;
}

var b = new Box();
b.Size = 10;
Console.WriteLine(b.GetSize());

A 5

B 10

C Compilation error

D 0

💡 Hint

The property sets the private field, and GetSize returns it.

The write-only property 'Size' sets the private field 'size'. After setting b.Size = 10, calling GetSize returns 10.

🔧 Debug

expert

Why does this read-only property cause a compilation error?

Identify the cause of the compilation error in this code snippet.

C Sharp (C#)

class Counter {
    private int count;
    public int Count {
        get { return count; }
    }

    public void Increment() {
        Count++;
    }
}

A The Count property causes a stack overflow due to recursive get/set

B The Count property cannot be incremented because the set accessor is private

C The Increment method syntax is invalid

D The Count property is missing a set accessor

💡 Hint

Consider what happens when Count++ is executed with this property implementation.

The property 'Count' has only a get accessor (read-only). Count++ requires both get and set accessors: it reads the value then assigns the incremented value back. Without a set accessor, it causes a compilation error.

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