🧠 Constructor Chaining and Inheritance in C#: What Gets Printed and Why?

Constructors are often overlooked when we talk about object-oriented programming, but understanding how they interact — especially across base and derived classes — is critical. Here's a short but powerful challenge that explores constructor chaining and inheritance in C#.

Let’s analyze this snippet and predict the output.

🔍 The Challenge

private class Program
{
	public static void Main()
	{
		ClassA refA = new ClassA();
		ClassB refB = new ClassB();
	}
}

class ClassA
{
    public ClassA() : this(10)
    {
        Console.WriteLine("apple");
    }

    public ClassA(int pValue)
    {
        Console.WriteLine("banana");
    }
}

class ClassB : ClassA 
{
    public ClassB() : base(0) 
    {
        Console.WriteLine("tomato");
    }
}

🧠 Step-by-Step Execution

1️⃣ First Line:

ClassA refA = new ClassA();

• This calls the parameterless constructor of ClassA:

public ClassA() : this(10)

• Which means it first calls the constructor with int parameter:

public ClassA(int pValue) { Console.WriteLine("banana"); }

• Then, after that finishes, the parameterless constructor prints:

Console.WriteLine("apple");

✅ So this line produces:

2️⃣ Second Line:

ClassB refB = new ClassB();

• ClassB is a derived class that explicitly calls:

  public ClassB() : base(0)

• Which invokes the same ClassA(int) constructor that prints:

  banana

• Then the body of ClassB's constructor runs:

  Console.WriteLine("tomato");

✅ So this line produces: 

       banana
       tomato