queries.cs

public Portfolio GetPortfolioById(int id, String period = "live")
{
    var portfolioQuery = _context.Portfolios.Where(p => p.Id == id);

    Portfolio portfolio;

    switch (period)
    {
        case "live":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, Live = p.Live }).FirstOrDefault();
            break;
        case "1d":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, OneDay = p.OneDay }).FirstOrDefault();
            break;
        case "1w":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, OneWeek = p.OneWeek }).FirstOrDefault();
            break;
        case "1m":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, OneMonth = p.OneMonth }).FirstOrDefault();
            break;
        case "3m":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, ThreeMonths = p.ThreeMonths }).FirstOrDefault();
            break;
        case "ytd":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, YTD = p.YTD }).FirstOrDefault();
            break;                
        case "1y":
            portfolio = portfolioQuery.Select(p => new Portfolio { Valuation = p.Valuation, OneYear = p.OneYear }).FirstOrDefault();
            break;
        default:
            return null;
    }

    return portfolio;
}