Program.cs

var calculatorFactory = new CalculatorFactory();

var adder = calculatorFactory.GetCalculator(CalculateType.Adder);
adder.Calculate(1, 2);

var multiplier = calculatorFactory.GetCalculator(CalculateType.Multiplier);
multiplier.Calculate(4, 2);


public enum CalculateType
{
    Default = 0,
    Adder = 1,
    Multiplier = 2
}

interface ICalculator
{
    void Calculate(int val1, int val2);
}

class CalculateMultiplier : ICalculator
{
    public void Calculate(int val1, int val2) => Console.WriteLine($"{val1} * {val2} = {val1 * val2}");
}

class CalculateAdder : ICalculator
{
    public void Calculate(int val1, int val2) => Console.WriteLine($"{val1} + {val2} = {val1 + val2}");
}

class CalculatorFactory
{
    public ICalculator GetCalculator(CalculateType type) => type switch
    {
        CalculateType.Adder => new CalculateAdder(),
        CalculateType.Multiplier => new CalculateMultiplier(),
        _ => throw new Exception()
    };
}