CalculadoraStrategy.cs

public class CalculadoraStrategy
{
    public enum Operacao
    {
        None,
        Sum,
        Sub,
        Mult,
        Div
    }

    private readonly ContextStrategy<int, StrcNumeros, Operacao> _contextStrategy = new ContextStrategy<int, StrcNumeros, Operacao>();

    public CalculadoraStrategy(string operacao)
    {
        Operacao op = Operacao.None;

        try
        {
            op = (Operacao)Enum.Parse(typeof(Operacao), operacao, true);
        }
        catch (ArgumentException)
        {
            Console.WriteLine("Operação inválida!");
            return;
        }
            
        _contextStrategy.AddList(Operacao.Sum, new Sum());
        _contextStrategy.AddList(Operacao.Sub, new Sub());
        _contextStrategy.AddList(Operacao.Mult, new Mult());
        _contextStrategy.AddList(Operacao.Div, new Div());

        SelecionarCalculo(op);
    }

    private void SelecionarCalculo(Operacao operacao)
    {
        _contextStrategy.SetStrategy(operacao);
    }

    public int Calcular(int numero1, int numero2)
    {
        return _contextStrategy.Execute(new StrcNumeros() { Numero1 = numero1, Numero2 = numero2 });
    }
}