考虑以下几行代码:
//prodProdGroup is a list within the itm object that I need to search. The items
//within the list are of type ProductionCostCalcHelper. I need to find one
//of the ProductionCostCalcHelper records in the list, calculate its total dollar value
//and assign it the value
ProductionCostCalcHelper prodGroupItm = itm.prodProdGroup.SingleOrDefault(f => f.MAST_PROJ.Trim() == laborItm.MAST_PROJ.Trim());
ProductionCostCalcHelper prodGroupItm2 = itm.prodProdGroup.SingleOrDefault(f => f.MAST_PROJ.Trim() == laborItm.MAST_PROJ.Trim());
if (prodGroupItm != null)
{
prodGroupItm.TOTAL_DOLLAR = avgDollarsPerHour * prodGroupItm.HOURS;
}
我假设SingleOrDefault方法会通过引用返回对象,但事实并非如此。更改ProdGroupItm的TOTAL_DOLLAR数量后,ProdGroupItm2保持不变,证明它们没有引用列表中的内容。为什么是这样?有没有办法更新列表中对象的值?
答案 0 :(得分:1)
如果您的ProductionCostCalcHelper
类型是可变struct
,则会发生这种情况
不要那样做; mutable structs are evil
每次传递struct
时,整个值都会复制到您传递给它的任何地方。
改为使用班级。