Methods that operate on state in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this C# code that modifies object state?

Consider the following C# class and code snippet. What will be printed to the console?

C Sharp (C#)

public class Counter {
    private int count = 0;
    public void Increment() {
        count++;
    }
    public int GetCount() {
        return count;
    }
}

var c = new Counter();
c.Increment();
c.Increment();
Console.WriteLine(c.GetCount());

A 0

B 1

C 2

D Compilation error

💡 Hint

Think about how many times the Increment method is called before printing.

The Increment method increases the count field by 1 each time it is called. Since it is called twice, the count becomes 2.

❓ Predict Output

intermediate

What does this method return after modifying the object's state?

Given the following C# code, what will be the output?

C Sharp (C#)

public class BankAccount {
    private decimal balance = 100m;
    public void Withdraw(decimal amount) {
        balance -= amount;
    }
    public decimal GetBalance() {
        return balance;
    }
}

var account = new BankAccount();
account.Withdraw(30m);
Console.WriteLine(account.GetBalance());

A 100

B 70

C 30

D Compilation error

💡 Hint

Subtract the withdrawn amount from the initial balance.

The initial balance is 100. After withdrawing 30, the balance becomes 70.

🔧 Debug

advanced

Why does this method fail to update the object's state?

Examine the code below. Why does calling Reset not change the value field?

C Sharp (C#)

public class Data {
    private int value = 10;
    public void Reset(int value) {
        value = 0;
    }
    public int GetValue() {
        return value;
    }
}

var d = new Data();
d.Reset(5);
Console.WriteLine(d.GetValue());

A The method parameter <code>value</code> shadows the field, so the field is not changed.

B The field <code>value</code> is readonly and cannot be changed.

C The method <code>Reset</code> is private and cannot be called.

D The field <code>value</code> is static and must be accessed differently.

💡 Hint

Look at the parameter name and the field name. Are they the same?

The method parameter value hides the field value. Assigning value = 0 changes the parameter only, not the field. To fix, use this.value = 0;.

📝 Syntax

advanced

Which option correctly defines a method that changes object state?

Which of the following method definitions correctly updates the count field in a C# class?

A public void Increase() { count++; return count; }

B public void Increase() => count + 1;

C public int Increase() { return count + 1; }

D public void Increase() { count = count + 1; }

💡 Hint

Remember that methods that change state usually have void return type and update the field directly.

Option D correctly increments the count field. Option D does not assign the incremented value. Option D returns a value but does not update the field. Option D tries to return a value in a void method, causing a syntax error.

🚀 Application

expert

How many times is the object's state changed after this sequence?

Given the following C# class and code, how many times is the value field changed?

C Sharp (C#)

public class Tracker {
    private int value = 0;
    public void Update(int newValue) {
        if (newValue != value) {
            value = newValue;
        }
    }
    public int GetValue() => value;
}

var t = new Tracker();
t.Update(5);
t.Update(5);
t.Update(10);
t.Update(10);
t.Update(5);
Console.WriteLine(t.GetValue());

A 3

B 5

C 4

D 2

💡 Hint

Count only when the value field actually changes.

The Update method changes value only if the new value differs. The changes happen at calls with 5 (from 0), 10 (from 5), and 5 (from 10), totaling 3 changes.