Custom method

public OutputClass GetOutput(InputClass input)
{
    OutputClass output = new OutputClass();

    double sum = 0;

    foreach (double val in input.tubeValues)
    {
        if (val % 2 == 0)
        {
            output.warningsCards.Add("Divisible by 2!");
        }

        if (val % 3 == 0)
        {
            output.warningsTubes.Add("Divisible by 3!");
        }

        sum += val;
    }

    output.result = sum.ToString();

    return output;
}