private IEnumerable <OrderViewModel> GetFilteredSales(IEnumerable <OrderViewModel> sales, OrderFilter filter)
{
var expression = filter.ToExpression();
var predicate = expression.Compile();
if (filter.ProductName != null)
{
sales = sales.Where(x => predicate(x.ProductName, filter.ProductName));
}
if (filter.ClientName != null)
{
sales = sales.Where(x => predicate(x.ClientName, filter.ClientName));
}
if (filter.Date != null)
{
sales = sales.Where(x => x.Date == filter.Date);
}
return(sales);
}