You have to explicitly provide the default value of the parameter in the lambda expression.
var data = DB1.view_items_stocks_ranges_prices_noserials.Select(s=> new
{
s.DetunitID,
MaxPrice = Convert.ToDecimal(s.MaxPrice).GetDecimalParts("."),
s.MinPrice,
s.NOSStoreID,
s.percent,
s.stitems_Code,
s.stitems_ID,
s.stitems_Name,
s.stitems_Status,
s.stitems_Type,
s.Stock,
s.UnitName
}).OrderByDescending(u => u.percent).Where(u => u.stitems_Status == 1);