C# Linq语句问题

我有以下代码，我想将for eaches转换成一个linq语句

        decimal originalCharges = 0;
        List<int> rdns = new List<int>()
        {
            1,
            2
        };
        foreach (var customerOrder in list)
        {
            foreach (CustomerBillTo billTo in customerOrder.BillTos)
            {
                originalCharges += billTo.Charges
                    .Where(charge => rdns.Contains(charge.RateCodeRdn))
                    .Sum(charge => charge.Amount);
            }
        }

这给了我一个错误，无法将类型“void”转换为“decimal”

我想我对如何处理原始电荷的+=感到困惑，就像我在第一个示例中的原始forEach循环中所做的那样

这可以在linq语句中完成吗

originalCharges = list.ForEach(co => co.BillTos.ForEach( ));

---

您只需将费用金额投影到并平铺，然后将其相加

var originalCharges =
    (from customerOrder in list
    from billTo in customerOrder.BillTos
    from charge in billTo.Charges
    where rdns.Contains(charge.RateCodeRdn)
    select charge.Amount).Sum();

或者，如果您更喜欢流利的方法：

var originalCharges =
    list.SelectMany(customerOrder =>
        customerOrder.BillTos.SelectMany(billTo =>
            billTo.Charges
                .Where(charge => rdns.Contains(charge.RateCodeRdn))
                .Select(charge => charge.Amount)
        )
    ).Sum();

A将很有帮助，这样我们可以确保提出的解决方案产生相同的结果。

var originalCharges =
    list.SelectMany(customerOrder =>
        customerOrder.BillTos.SelectMany(billTo =>
            billTo.Charges
                .Where(charge => rdns.Contains(charge.RateCodeRdn))
                .Select(charge => charge.Amount)
        )
    ).Sum();